PayPal login Website: https://web.sites.google.com/view/paypalsigninlogin/ There could be a number of reasons why you might be seeing this error on your screen while trying to log in. But at the same time, you should also check for any typo mistakes while entering the PayPal login credentials on the login portal. Whenever a PayPal merchant user logs in to his account, some information sent through his account is highly case-sensitive. Therefore, you must check each detail carefully before proceeding to the next step.