1.Please confirm whether the account is registered or not. 2.Check that the letters are spelled correctly in both upper and lower case 3.Please distinguish between TeraBox account and third - party accounts like Google, FB and Apple.For Google / FB / Apple accounts, please log in at the third party portal. If the above answer does not solve your problem, please go to the user feedback page and attach a screenshot of the problem.We will locate and solve the problem as soon as possible.