BuddyPress.org

I have this site: https://prodicallearning.com/
When a user registers this site he gets an activation email with activation URL and key.
But when the user enters the key it shows Error: “COULD NOT CREATE USER”.
And when I try to register again with the same email it shows “Email Already exists”.
When I try to login by the same credentials it shows ” There is a problem with the username and password”.
When I again visit the activation page it shows user already activated. But the users are not listed anywhere.
Current WordPress version: 5.4.2
Buddypress version: 2.6.5
Theme using : WPLMS by Mr.Vibe

I don’t know what is happening with the site. I am really stuck at this. A quick response will be appreciated.
Have a good day.