If a respective User's account has been deactivated, but you now want to make it active again, follow these steps:
1. Go to the Configuration → User Management page.
2. Use filters to find the user.
3. Set the filter “Active” to “No,” it will allow you to see inactive users.
4. Once you have located the respective user, click on the Edit button.
5. Then, you will see the “Edit User” menu. Find the switcher at the bottom of the main page, click on it, and hit the Update button. Now your user is active again.