which one is the right to you use it in the negative past sentence
he couldn’t enter the correct password .
Or
he didn't enter the correct password .

Question

which one is the right to you use it in the negative past sentence
he couldn’t enter the correct password .
Or
he didn't enter the correct password .

Answer

"He couldn’t enter the correct password" = he was not able to.

"He didn't enter the correct password" = a fact. Perhaps he knew the password, but entered something different. We don't know if it was correct or not.

Answer

Both sentences are correct.