If you wish to reactivate or simply find an inactive user, you can go to Settings and click Users. From there, you need to click the Status filter and tick Inactive. This will show you a list of your workspace's inactive users.

If you wish to reactivate a user, you can click on the Actions button on the same row as the user's name and click Activate user.

Once a practitioner user has been deactivated, appointments will remain although a deactivated practitioner's calendar will no longer be displayed. If you wish to deactivate a practitioner's account, you may want to either re-assign their future appointments or archive them before deactivating.