I have some blogs, and after upgrading to 5.1.1 I always have to reauth myself. If password/username is wrong, I got that error message but if I enter right data, the page simply reloads. So I go to:
it then redirects to:
and even I enter the right account data, it just reloads the site.
Of course, clearing all browser data helps - but next day, this bug occurs again. I dont think its a good solution to clear my browser everytime when it happens.
EDIT: Its Php 7.3 and nginix
EDIT2: I added this line to my config:
so far works well. I dont know what it is by the way.