Microsoft Graph - PopAuthenticatorInvalidSignature errors when patching to calendar events

This was a server side issue that's now been rectified.

I've seen this exact issue across multiple customers' Graph applications. It's been sporadic since at least yesterday and as of roughly 17:30 Central today, it's stopped happening completely. It certainly looks like some sporadic API outage/issue.

We have not re-registered any applications - it just stopped failing on its own. We've encountered this issue with apps that have been registered with both the old and the new app registration system, so I don't think it's related at all.

I read the deprecation notice on the old app registration portal as saying that the old portal is deprecated, not that any previously registered apps are deprecated and need to be re-registered. Microsoft would never silently break nearly everyone's API access like that.