I (or someone) created a subfolder inside a folder but I cannot see it

The person that called us had full access to a shared mailbox and created a subfolder called “Abe's Folder” but couldn’t see it listed in the folders on their Outlook, even though some others could

When connected to their PC, in Outlook, the Download shared folders setting was enabled (under Account Settings → Change → More Settings → Advanced tab) – here’s an example of it:

Using Cached Exchange Mode is not a problem, but the ‘Download shared folders’ setting can be a problem – there are many references to it causing havoc, especially with larger shared mailbox (~ 2 GB) There’s no value in trying to cache a large shared mailbox locally, and it has caused problems in the past.
If you have weird issues such as this  -- especially on shared mailboxes – clear the ‘Download shared folders’ setting, save the changes,  and restart Outlook.