We have the same issue over here, Hp M604,M605,M601 are going on and offline over the last week.  This started Oct. 30.  Came back online Thursday the 2nd. and now have been offline again this week starting yesterday.  This in ONLY affecting HP printers.  Our samsung printers are working just fine.  ALl printers are hooked up over the internet with there built in google print.

Monday morning now an still no change.

There is a post on HP's support forum with a work around.  

https://h30434.www3.hp.com/t5/HP-Connected-Mobile-Printing-and-Cloud-Printing/Google-Cloud-Print-shows-offline-on-all-Cloud-Ready-HP/td-p/6404594/highlight/true

Seems like issue is related to Hp M604,M605,M601 printers,that are cloud print capable printers.Requesting someone from the CloudPrint team to look into this issue for further triaging.
Thanks..!

Exact same issue on all of our HP LaserJet 400 M401dw, and HP LaserJet M402dw printers.

Same issue with one of my customers, I hope to hear people from CloudPrint to help us. Thanks!

Jay, could you please help triage this issue ?

I had a similar experience as noted above where it stopped working and then started working again a few days later and then has stopped working for several weeks now.  I also have HP LaserJet 500 color M551, HP LaserJet 600 M601, HP LaserJet 700 color MFP M775 and HP LaserJet M402dw that are experiencing this issue (all 30 of our HP printers on Google Cloud Print).  I also found that printers from Xerox are still online on Google Cloud Print and printing fine.  I also observed that all HP printers went offline on the same day (even ones that are in a different city with a different Internet provider).  I opened a ticket with HP and they have found no issues with regard to their services and have advised that this is probably an issue on Google's end.

This is what I was told by HP.  They do NOT want you to use the Google print function built into the printer any longer.  They want you to turn on Hp Web Services and then connect the printer via https://www.google.com/cloudprint/learn/setup-hp.html

Here is there official document on the subject.
https://support.hp.com/us-en/document/c02817255

All of our printers are back up and working but I had to reconnect all of them.

This work-around does work, but requires more time and puts us completely
at the mercy of HP. I also see that, with our agreement, it gives them
access (ownership rights?) to all of our clients, staff, and student
material. If this is something HP is enforcing without notice I have some
concerns and may be recommending other solutions.

So I completed the setup for the print and it seems to only work for me.  I was trying to manage the printer by device in an OU so that the guest login could also print.  I didn't really want to share each printer will all of my students and have them pick which one they are printing to.  

Am I missing something?  

I removed the printer from cloud print and then re-added it to https://www.google.com/cloudprint/learn/setup-hp.html via e-print then removed the old queue from https://www.google.com/cloudprint/#printers and renamed the printer that show up.  When to Admin console in device mgmt. and removed the old printer and re-added the new print in cloud print.

So I checked my printers today and I saw jobs had gone through the queue.  I checked the devices and the print queues are finally showing back up again.  I'm not sure what is different or if it just takes some time for the printer to show up after being added via eprint method but it seems to be working at this time.  Thanks for all of the assistance.

FWIW - I have found that printers set up in the morning via ePrint show up
right away, but by noon or so it takes about a day for them to appear.

The descriptions above describe my situation with an HP OfficeJet Pro 8720. It shows 'Offline'. I have deleted and re-registered this printer, and it comes up as 'Offline'. I find I can get print jobs done if I power-cycle the printer.

We experienced this on about 60 HP Color LaserJet M452dn.  I echo the above findings that HP's service seems to be a work-around, but not one that I find acceptable.  The aforementioned privacy/security issues of third-party handling are huge.  We invested in these devices SPECIFICALLY to bypass third-party services.  I hope this gets addressed soon.

HP 8710 (actually a Costco "8715" that calls it self an 8710) here. GSP worked fine and reported printer Online for a month or so after first setup. Now, last two weeks or so, printer's embedded web server reports printer is "not connected" to GCP, and GCP Printers page reports printer is "offline". Despite this, print jobs still get through. I don't think this is a Chromium problem or a Chrome problem or a Chrome OS problem. Something in HP ePrint/GCP -ville has changed in the last several weeks. HP? Google? Who's to say? Where is there a queue to report problems to Google Cloud Print? I talked to HP Connected Support for 48 minutes and the moment I said that jobs do print to the "offline/not connected" printer, they said it can't possibly be an HP problem, contact Google. Sigh.

Same issue here, to new GCP-enabled Brother printers (DCP-L2520DW and MFC-J5620).

It has worked perfectly for some months, but now both printers randomly goes offline. Power-cycling printers doesn't bring them back online :-(

In the printers web admin page, they appear to be "disconnected" from Google Cloud Print. Had to register them again. That's when I had a massive headache trying to re-register both printers.

One (the MFC-J5620DW) would reconnect with success, but the other one (DCP-L2520DW) would never complete the registering process. Once I sign with my google account on the browser, GCP tells me that the printer has been added to the account ; indeed, when going to GCP printers list, it appears. But when I check the Brother printer web admin page, it says in red "error" and the printer is still unregistered in the printer web admin.

Tried unregistering all printers, check date/time on printers (MFC-J5620DW has a date/time value, and it's correctly set ; DCP-L2520DW does not have any date/time value, so can't set it...), power-cycling printers, etc. No success, printers are offline as soon as they are powered-cycled. 

Before the issue appeared, printers could be powered-off (at night, week-ends, etc.) and powered on, queued GCP jobs would print in seconds after powering on printers.

By googling with "brother google cloud print issues", I found some thread that advise to register through another browser that Chrome. In fact, I'm using Chrome as my main browser, with my personnal account signed-in in settings (to sync bookmarks) ; in the browser, 2 google accounts are used (gmail, agenda, etc.), the first one is my business account, the second one is my personnal account (the same that is used to sync bookmarks in chrome settings).

So I opened Firefox (no google accounts signed in), registered printers to my business account, and they are at last ONLINE ! Power-cycled them, still ONLINE ! 

Why on earth using Firefox instead of Chrome as the browser to go to printer web admin page could change the registration process issue ??? Maybe Chrome is messing with google accounts already signed (+ google account in settings) ? Should have tried to register the printers through their web admin page and a private tab, so no google cookies/opened sessions could interfere.

Saw on Google that some printers have obsolete certificates and that could be a problem. Hope this is not the case, as Brother has not released any new firmware for one year...

I will monitor the OFFLINE/ONLINE issue and update this thread if necessary.

Any updates on this please? We have two cases still waiting for an update on this. Thanks!

I suspect this is related to  crbug.com/798706  and potentially b/71678287.

We use papercut to connect our mfps to google cloud print. It does seem to work if you print anyway but users are obviously confused. 

Google Cloud Printing is anything but difficult to use and rather helpful, it isn't great. Since you need to buy a Google Cloud Ready Printer (with a huge amount). Also, if your printer isn't Google Cloud Ready, it must be attached to an always-on desktop machine that is associated with your Google account. Although you can go with Brother Printer Support to know more and troubleshooting help website https://www.printererrorrepair.com/brother-printer-support-phone-number/