Tested this issue on reported version 66.0.3359.117 & Canary 68.0.3400.0 using  Win-10, Mac 10.13.3  and followed the given steps,

Steps
-----------
1. Installed browser extension given in the original comment.
2. Clicked on Background page link in chrome://extensions page.
3. Entered the given code into the console.
4. Observed that the page is navigated to ""Complete your purchase"" page 

@Reporter: Here it is asking for Payment, we don't have testing card's to verify this issue. Can you please tell us any other way to test this issue? Or is there any simple test case available to check this issue from our end. 

Thanks

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Hi Phanindra,

I've added your email address, phanindra.tm@gmail.com, as a tester, so you will not be charged for the transaction.

To verify, please read the official testing docs: https://developer.chrome.com/webstore/payments-iap#testing

Just so you know, it's using the official Google Merchants/Payments system, and the Payments API. https://developer.chrome.com/webstore/payments-iap

In any case, notice it said "Billing starts Apr 27", the payments don't start for 7 days because it has a demo, so even if there's an error, you still won't be charged and we can cancel it right away.

Please let me know how else I can help.

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Unable to test this on reported version 66.0.3359.117 because we are getting 404 & 405 errors while using URL provided in  original comment  

Attaching screenshot for reference.

" WebStore page: https://chrome.google.com/webstore/detail/copiedin/jgiejpldlcmmopmojhhnjgidjcijbbla " & 

"https://payments.google.com/efe/payments/oauth/embedded/buy_flow/submit?"

Steps
-------
1. Logged in to chrome account using phanindra.tm@gmail.com
2. Entered the webstore page URL
3. Still observing error 404

 @Reporter: Could you please let us know is there any other option available to install this extension? If possible could you please send the extension as an attachment folder to check this issue from Chrome testing team.
 
Thanks!

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Hi,

It's because you're not signed into your phanindra.tm@gmail.com account on the webstore.

I've made a video demonstrating how to fix this. The video shows that I also got the 404 error because I was not signed into the correct account, but after signing in, the 404 error goes away and I can download the extension.

https://www.useloom.com/share/177f52f0e6f149339f556d8f68d0731f

Please let me know if you have any other questions.

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Unable to purchase the app as we are getting Invalid card details Error.

@Reporter: Tested the issue by providing multiple dummy cards from the url as given bellow:

1. https://www.datatrans.ch/showcase/test-cc-numbers,2.http://www.getcreditcardnumbers.com/. 

we have tried all cards which are in mentioned in the sites as we couldn't move furhter to test this issue, so can you help us to test this to furthermore.

Thanks!

Phanindra where did you find that credit card URL? It's not mentioned in the official testing documentation.

https://developer.chrome.com/webstore/payments-iap#testing

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Phanindra, the Google backend service is the one that processes your card information. IF you're getting "Invalid card details" Error, that's the GOOGLE BACKEND telling you that. There's literally nothing I can do to change that.

Phanindra, I will literally send you $5 via Google Pay if it means you'll properly test this. I'm pleading with you to please help

Adding proper component and requesting rouslan@ for help in triaging this further.

Looks like rouslan is OOO, ccing mathp@ as well for inputs on this.

Durga, will it be possible for you to find someone from Payments team to followup on this bug.

As per comment #17, adding 'TE-NeedsTriageHelp' label and requesting durgapandey@ to look into the issue and help in further triaging.

Thanks...

I'll send an email to the Google Payments team for triage (this is the Chrome browser bug tracker).

Over to Devlin since this is an extension API. 

jawag@, seems like something on the payments backend.  Do you know who owns this?

I think it's possible this could be a bug in the CWS Payments code. +phu@, could you take a look and if everything looks ok, we can send to the Payments team to investigate.

I was able to buy the in-app product without a problem... Could the developer please try again and provide the login account if it can still be reproed? Also, please note the owner's account probably can not purchase her/his own products.

Well I tried to purchase it again as before, and I got the following:

{"srp":[["An unexpected error has occurred. Please try again later.",null,"56c2f8ad90f28"] ... (a bunch of other stuff)


Then I opened up Chrome Canary and logged into a different account, ran through the steps, and the error didn't occur. This means either developers in general get this error when trying to buy their own product, or it's just something with my account (hello@wyatt.engineer). Either way, is that really an "Unexpected error"? And wouldn't you agree the returned text is really unclear? Finally, as far as I know this isn't documented anywhere that you can't buy your own products.

yeah, developers can't buy their own products. We can look into improving the returned messages, and make sure it's documented clearly as a first step.