"you" could be translated to "ön" and "te", it's not clear here.
And so both should be accepted. (If not, report the missing alternative(s), please.)
This could be a stupid question, but why not "Vagy László?" or "László vagy?"?
"László vagy?" is definitely accepted. "Vagy László?" sounds a bit weird. Ön is a formal addressing.
"te" is a correct translation of "you" in this sentence
Te László? is still marked as wrong answer by now.
"*Te László?" is incorrect. If you have anything else than a 3rd person (ő, ők, ön, önök) as a subject, you need to include the respective form of the verb van: