I would definitely call back and escalate to a supervisor. And keep escalating if needed. At a bare minimum, you are entitled to downgrade compensation plus fare difference. They should, however, move you back to PS. Look
to see if the ticket was ever actually reissued after the downgrade. If not, that will give you more leverage.

Pre-Covid we had a trip with a similar PS issue. We finally got downgrade compensation and fare difference for C+. It was a hassle. After that experience I decided I will not book PS again until all fleet types have it and the issue is somewhat minimized.