Outlook Shared Mailbox

Good morning all!

I have a weird issue going on with one of my clients, shared mailboxes.

They are unable to create a folder on user 1 and see it on user1's computer. If you calculate the folder size, you can see that the folder they created is there. But is not visible on anyone's machine.

I would like to say its probably a caching issue, but they mailbox is about 26gb so it would be pretty inconvenient to have to load that every time + their own mailbox.

Any info on how the server should cooperate or regarding a fix please feel free to email me or send a message

Thanks in advance!