Workspace admins can reactivate any users who have been deactivated right from workspace settings. Deactivated users are hidden by default and you can make them visible and manage them by using the triple dot menu.
Select your workspace logo and go into Manage users. Click on the triple dot menu at the top right corner of the page and select Show inactive to view all deactivated users.
Scroll down the list of users to view the inactive users. Click on the the triple dot menu next to the inactive user's name and select Reactivate User.
Note: Once a user is reactivated they will regain access to all their past notes and meeting streams. No information is lost!