Hi,
it can be due to different cause, without seeing the behavior I can only think that you have enabled option "Force the compilation of required fields" in Easy Profile options (Components->Easy Profile->Options). With this option after login you cannot navigate in the site until you have filled all required fields.

Normally when this happen then you should see a error message that describe the cause....if it is not so then it's possible that your template have some problem with Joomla error messages (you can test it by trying a login with wrong credentials and check if you see a error message).

Including getting an error that the email is used in an edit screen

Have you some error/info message in Components->Easy Profile? if yes then please try to follow instructions.
Also please try to check if you have a menu item of type Users->Edit User Profile.