...

1. Click show disabled users
2. Search to find the disabled users
3. Check the box in front of the disabled users
4. Click "Enable" to enable the user 

Rules to trigger the disable function:

All of the following conditions have to be met at the same time to trigger the auto user disable function.
1) Non-client portal users
2) Non-manual enable users
3) Non-super admin
4) Non-super tenant
5) Active account
6) No created mapping connection between system user with Connectwise or Autotask account
7) No first name or last name
8) No job title