I have two users within the company that seem to be running into an issue each time they try to access the public folders.
They receive the following message: Cannot expand the folder. The set of folder cannot be opened. Microsoft Exchange is currently busy. If this message is still displayed in 30 minutes, contact your Exchange Administrator.
I have assigned the same public folder access to myself and it seems to work fine for me.
I cannot seem to find the public folder within the owa version of outlook either, for the users in question.
I have removed the user's access and waited for about 2 hours, reapplied access to the folder and still nothing.