I'd also add that I had a similar experience with physical therapy (PT) after surgery. When I changed insurers from BCBS to Fidelis (just a month or so after surgery), I found that the PT group I was using didn't accept my new insurance.

It's sad that we have to jump through all sorts of hoops just to get the medical care we need. Which is often the case even when it isn't an edge case like yours (or mine with my PT -- my situation was, of course, much less consequential since there are many PT providers out there).