Shared mailbox not syncing with OUtlook 2016

Office 365 user can't sync with shared mailbox. Mailbox is actually down as a "Resource" in 365 and the user used to be able to sync all foders. However, it had stopped so i rebuilt the OST. Now, the mailbox is visible in the right hand side panel, but none of the folders have synced.

Any ideas?

Using Outlook 2016.
ICT EngineerAsked:
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Andy MConnect With a Mentor Internal Systems ManagerCommented:
If you set Outlook to non-cached mode for the shared mailboxes does any data/folders show up?
Vasil Michev (MVP)Commented:
It can take some time for folders to resync after rebuilding the OST, especially if the profile is large. How big is the shared mailbox? And how big is the "primary" mailbox, do you have any other shared mailboxes added? How big is the OST in general?
ICT EngineerAuthor Commented:
@Vasil, yes there are other shared mailboxes attached. It's nearly two days now without updating, so don't think it's a time issue. The OST is currently 8GB. The old OST was 11GB and i know the missing shared mailbox data is about 2GB.
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Vasil Michev (MVP)Connect With a Mentor Commented:
The size isnt that big, but it can still be a problem on older hardware. I would advise creating a new profile with just the shared mailbox added in it, and taking advantage of the "cache slider" option to reduce the amount of data kept locally. Or you can access it in Online mode (uncheck the "download shared folders" option).
ICT EngineerAuthor Commented:
@Andy that seems to have worked. Set shared mailboxes to non-cached mode and the mails appeared.

Any ideas why this happens? If they go offline, I guess they won't be able to see anything?
Andy MInternal Systems ManagerCommented:
Seems like a cache/profile issue if emails are fine in non-cache mode.

As Vasil has suggested - next step would be worth trying a brand new profile and seeing if the problem persists there.

Generally I don't have shared folders in cached mode as it does tend to have issues with syncing (plus can use a lot of space if you have multiple mailboxes) though as noted, if the server or workstation is offline you won't be able to see emails in non-cached mailboxes.
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