I use the PayPal Authenticator and with the current PayPal checkout form, I'm unable to log in. I've used Safari, Chrome and Firefox browsers and had the same experience.
If I wait for the token to expire, PayPal will provide me with a different login page, which does work. Otherwise, I enter in my password and the page reloads asking for the password over-and-over. Thankfully, I discovered a work around and was able to successfully log into PayPal, but it was very frustrating to say the least.
Don't know if I'm the only one experiencing this issue, but I wanted to at least make you aware of it.