It doesn't matter where the company that pays you is located. What matters is where you do the work.
There was no rule change. You do need to find another tax prep person, other than the one who never told you that you have to file in each state that you work in. But you are already looking for someone new. The person that you spoke to is on the right track, but it would be best to find someone who specializes in multi-state taxation. Ask around among people you work with. Performers and other people in the entertainment and sports industries deal with this all the time.
