"You are therefore no more a doctor" should also be an accepted translation!
It's a bit too literal, if you look at it you can see that rearranging it to "Therefore, you aren't a doctor anymore" sounds far better as, while your sentence makes sense, nobody would actually say it in English.
I believe you threw in an extra "are" by accident.
It's grammatical in English, and since it's not a course in English or Translation, it's fine if it's too literal for it to feel natural in English.
The point is figuring out what's said in German.
(and it's already accepted BTW)
I translated it as "You are therefore no longer a doctor" and it was accepted. Consider me pleased.
Apparently one of the five bajillion "My answer should be considered correct" responses I sent found an audience!