In regards to what you are experiencing with DataAssist you may have a corrupt config, here are some steps you can take to get past this if it is the issue:
You could alter the User Registration Solution Pack to do this. You would want to use Universal Email and alter the verification email that is sent to the user. You would want to send this message to you instead. You can make the user active by updating the UserEmailVerified column in the db for that user. You should change it to a 1 to indicate the user is verified.
If you want a back end page to do that part you would need to have an update page based on your users table. DataAssist should be able to create the page for you, or if you create the update form yourself you can just apply the DataAssist Update server behavior.