admin locked out after setting up registration form

After some security issues with another registration form, I installed CM Registration Pro. I created a login form first, it showed up in Divi, and I logged out. Later, I could not reach my custom login URL (the website kept reloading) and I could not log in from the CM login form. I deleted the plugin in AMP and things returned to normal.
As I’m new to this plugin and it has many settings, perhaps I did something wrong.
Help would be appreciated.