Suddenly (about 18th Sept 2020) I can't log into my Admin and None of my customers can log in. I also cannot create a new customer account and cannot ask for a password reset.

ADMIN: When I fill in Username and Password (the complex log in given by AbanteCart - I never changed it) it goes to log in but instead returns to the Log in with no input info and no message of error.

When I log in as a customer I see:  Unknown error encountered. Please try again!

Was there a recent  upgrade that ruined the site?