M-Files mobile no longer working on iOS. "Attempted to perform an unauthorized operation"

I believe you already have a support case open for this, but I'll add some information here also for others to see.

M-Files Mobile requires the classic M-Files Web setup that enables M-Files Web Service (MFWS) so it doesn't need the new M-Files Web.

First you should check that the .NET Framework version on the server meets the minimum requirements: M-Files Web Access stops working after upgrade to 22.9 or later due to .NET issues

There was also a regression in the 22.8 release that sometimes causes authentication issues, the issue ID is 164701. This has already been fixed in our internal codebase and the fix will be included in the October release. As a workaround until then, if the VaultDNSConfig key is not yet present on the server, add an empty VaultDNSConfig key to the server registry and see if that helps: Configuring Mappings Between Incoming Connections and Vaults

It turns out we did have .net 4.7 but I upgraded to 4.8 anyways. At the same time I looked into your regression you mentioned, and that fixed the issue! Thank you for that!