Some users suddenly cannot access shared mailbox folders

Occasional Contributor

Hey folks,
Exchange online / OWA environment (fully online no hybrid) - have 20 or so users all accessing various shared mailboxes with various shared subfolders all with different permissions. All using OWA. This has been working absolutely fine until Monday morning when all of a sudden 4 users in various countries couldn't access the usual folders with permissions. Only way they can have access is by delegating full mailbox access which I can't do as there are restricted folders in those mailboxes which they don't have user permissions to.
Here's odd - make a brand new user with permissions - and they can' access either.
Make a new mailbox/share and those users can't access.
All permissions look correct through OWA mailbox permissions
All permissions look correct when adding the shared mailbox to Outlook desktop and querying permissions.
All permissions look correct when querying using Get-mailboxpermission and Get-MailboxFolderPermission through Powershell

Microsoft techs been on this since Monday and today we're trying New-MoveRequest but so far after 4 hours that doesn't seem to have fixed anything.

Even making a new licenced user and new shared mailbox/shared sub folders - still broken.
These users can 'see' the subfolders (as long as their permissions include 'folder visible') but cannot access. 
users can even create subfolders within those folder that they can't access, and then subsequently have no access to them, even though they are 'owner'

Any clues or even wild experiments to try, gratefully received !
Much thanks


2 Replies
Best work with support on this, I've seen few similar threads recently so it looks like something got broken on MS side.

@Vasil Michev Hey much thanks for that mate; yea they're keeping on it but I thought I'd see if anyone out in the world had any thoughts I could try coz it's moving with glacial slowness. Been 4 days now and users are grumbling. I'd be interested to see if those other threads are connected - I did have a quick search but couldn't see anything before I posted - will go digging some more.