I ran into the same problem. Having no support to solve the issue is disappointing.
I ran into the same problem. I have disabled hosting cache on Bluehost, deactivated WP-Optimize, Jetpack, etc., but still could not fix the issue. Simply the Ajax login does not work with Dashboard page. So even if it is already logged in, the Dashboard page will not show user data (stuck on the login screen) until a hard refresh.
