Login Issue after registration

Hi guys, I've been testing the site login and registration today for students. There are some issues happening. (You will be glad to know the WP SMPT email plugin is working now, so registration emails work). I have myself and someone else testing at the time same time whilst we screen shared. These are the two issues happening. 1. My friend tried to register, he got an activation email and clicked on the link, but it didn't automatically log him in. He tried to log in with the details he submitted, but it keeps saying that his email or password is incorrect. He also tried to log in on a mobile phone and still the same error. He even tried to reset his password. He got a password reset email, but it still wouldn't work. I also reset his password twice from the backend panel in his profile, and it still wouldn't let him log in. 2. I tried to register with my own different email, it automatically logged me into the account after I clicked the activation email. But when I logged out of the site and tried to log back in, I also get the same issue. It says my username and password are incorrect. Any idea what is going on, please guys? Please see the video link in the next private message. Kind regards Darren