I have already read thru the similar threads and tried them without success.
One user (of course the owner of the company) is getting the An error occurred and your request couldn't be completed. If the problem continues, contact your helpdesk with this HTTP Status code: 500 error code.
He is getting it using Safari, Chrome, and his Android phone.
I checked with other users - Chrome works fine - they too had the same message with Safari - but let's not get sidetracked with that.. let's stick to the boss cannot access OWA now. It was working. I did the setMailbox identity line - it replied that nothing was changed.
The only thing I can think of is that he exceeded his quota - so I bumped that up and am waiting to hear from him.