User cannot see database on Mac or PC despite being invited?

User cannot see database on Mac or PC despite being invited?

Hi all,
Another trivial question, apologies!
I have created 4 databases that I'm testing in the office. I have shared the database with 2 people. One of them can see the form fields no problem... but the one other user can get into the form but cannot see the form fields database itself. All he can see is the headers of the forms and views and the rest of the page is blank! I thought it was a problem with his aging mac so I asked him to bring in his laptop and its the same thing.
Obviously an issue with his account? So I "un-shared" him or deleted him from the databases and then re-invited him hoping to re initiate the "handshake" so I resent him an invitation but he still can't see the databases on both PC and Mac in either Firefox, Safari, or Internet Explorer. I checked my backend of the database and he is cleared to see and use all the databases?

Any advice on what I should do?

Cheers in advance!