I just spent two hours on phone with tech support, going round and round.  I kept insisting they MUST change the verification number for the old employee (in this case it was our main email address, but the ex employee's phone # as the verification #.  They told me to try this, try that, clear my cache (not it is NOT my cache that is the problem, it is INTERNAL to Quickbooks!!). FINALLY, after much insistence, they went in and did something behind the dark curtain and changed the main verification number as per my instructions. You need patience, perseverance, and insistence, and EVENTUALLY they will understand and do what needs to be done.

Good luck to all who experience this issue!