Either can be correct. What is the context?
Interested in Language
why didn't you submit your transcript or why you have not submitted your transcript
chiko, your previous threads show that you are capable of writing better English than this lazy effort, in terms of capitalisation and punctuation.why didn't you submit your transcript or why you have not submitted your transcript
Please edit your post to save us the trouble of doing so.
Additionally, please note that a better title would have been Why didn't you submit your transcript?
Extract from the Posting Guidelines:
'Thread titles should include all or part of the word/phrase being discussed.'