Update error code 30088-27 Office 2021 what to do to get corrected????

I tested using two methodologies.

I took a device inside my network behind Firewalls and Proxies and it failed.

I took the same device and plug edit into a home network without firewalls and Proxies and it worked.

We then used Fiddler and Wireshark to analyze the traffic and found that connections to Microsofts CDN when we invoked the Clicktorun were not using the WinInet Proxy.

Our Proxies were configured for Authentication for Microsofts CDNs. When we disabled Authentication, as is required for WinHTTP Proxy, the Click to run worked and our Office started to update. We've had 4000 Systems stuck on June's update for 2 months, As of today we've been able to patch 3000 systems with this firewall/proxy change.

This is not the kind of configuration the ordinary user would have here. I would assume most users here are on a home network and not an enterprise environment as you describe. Also, besides the fact that how does this explain some of the users having fixed the error, me included by other implementations mentioned here? Your knowledge is commended but I would be surprised that ordinary users will need to implement this type of change.

Can confirm that in a little different way. I use some local policies regarding office "privacy" - Office 2016 C2R.

Enabled the marked policies just for trying (were disabled)

Rebooted => Updates worked, no error 30088-27

Disabled the marked ones again.

Rebooted,=> Updates no longer work, again error 30088-27

Well, I think MS might call it a user error if one uses non- MS tools, but if they're stumbling over their own GPOs? (And yes, updated administrative template files for office)

Briefly for information.

Version 2408 16.0.17928.20066 is available on the release channel and the manuel update worked well so far now (at least for me). Release notes are following...

You can also update Office by using the following well known command line:

"C:\Program Files\Common Files\microsoft shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.17928.20066

I updated (elevated command prompt method) to Build 17830.20166 plus I installed the Patch Tuesday fare for Windows 10; KB5041580 and KB5042352.

Zero change; error code 30088-27 persists.

At this point, I'd settle for just an official statement from MS, to the effect, "We're investigating an issue that inhibits the update feature in the MS Office Suite of programs and Microsoft 365".

Hello everybody.

I've been following this thread from the beginning.

My Office 2021 has been affected by Update error code 30088-27 since Build 17726.20126. Today I updated to Build 17830.20166 using the manual procedure described in this thread. In the meantime, my Win 10 also updated to KB5041580 and KB5042352 ("Patch Tuesday").

After these updates, Update error code 30088-27 is gone. Puff! Just like that. Vanished just as mysteriously as it'd come.

Just wanted to let you guys know.

David