I think because build never runs (it expired before running), so Milo doesn't render it.

I'm keeping this bug open for hinoka@ to chime in if this is something we want fixed in Milo.
From my PoV, we don't want to :) Instead, we'll just fix lack of hardware  issue 856449 

Sorry I mistakenly took the buildbot bots out of the waterfall before the luci bots were ready.  Looks like the LUCI bots are working now, so I'll fix this by flipping it to LUCI.

The following revision refers to this bug:
  https://chrome-internal.googlesource.com/infradata/config/+/72066c546c0e8417bf2633d1da34319d00d1baee

commit 72066c546c0e8417bf2633d1da34319d00d1baee
Author: Ryan Tseng <hinoka@google.com>
Date: Tue Jun 26 21:45:47 2018

Similar things also happens on "Win7 Builder Goma Canary" builder?
Also "Win7 Builder (dbg) Goma Canary" builder has no machine in the the pool?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/29f4339a62bfe97edccdf4ebe4380a138ac7954a

commit 29f4339a62bfe97edccdf4ebe4380a138ac7954a
Author: Ryan Tseng <hinoka@google.com>
Date: Wed Jun 27 16:55:42 2018

[cr-buildbucket.cfg] Use win7 for Win7 Builder (dbg) Goma Canary

Bug: 856451
TBR: tandrii
Change-Id: I65a66a6a33e7a9751f2106a1f94a6e0c32120230
Reviewed-on: https://chromium-review.googlesource.com/1117208
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570815}
[modify] https://crrev.com/29f4339a62bfe97edccdf4ebe4380a138ac7954a/infra/config/global/cr-buildbucket.cfg