If a respective User's account has been deactivated but you now want to make it active it again, follow these steps:
1. Go to the Configuration tab —> User Management page.
2. Find the respective user (you can use a filter for searching by name or other parameters).
3. In the filter for “Active” choose “No,” which will allow you to see inactive users.
4. Once you have located the respective user, you should click on the Edit button.
5. Then you will see the “Edit User” menu. Find the switcher at the bottom of the main page, then click on it, and then hit the Update button. Now your user is active again.