I am also having the exact same problem.
Tried disabling Firewall. Even bought and opened a support ticket.. Been 3 days, first was told to disable selinux (it is also disabled).
I tried opening :2082 and :2083 from many different browsers and even VPN..
When I log in from root, this message appears: "WARNING: User Panel possible issue detected! If you have issues with user panel login, CSF Firewall stop/start will be needed. "
In Security -> User security, login security is also disabled
What to do
??