I resolved this problem. Found two solutions:

1. The error message appeared when I tried to log in to my PayPal account from the Firefox browser, but when I tried to log in using the Chrome browser there was no error message and login was successful.

2. I am using the Bitwarden password manager in Firefox. When I logged out of Bitwarden, I was able to log in to PayPal with no problem. To log out of Bitwarden, open the Bitwarden window and choose Settings from the bottom of the screen, then scroll down and choose Log Out.