I am getting the below error at the time of importing data.
Sorry, no account could be found related to the email/username and password you entered.
Welcome to the community.
From the documentation:
Select the file you uploaded. Enter the email of the user from your legacy forum you want to be the superadmin of the new forum. Check “Use my current password”. Leave the password box empty.
Are you entering a valid email address/password from you old forum?
What version of vB are you importing?