Admins can un-archive both teacher and admins user accounts in Assist.
Step 1: Click on users
Step 2: Enter the details in the dialogue box to search the user
Step 5: Under status, change to archived
Step 3: Select the user you wish to un-archive by clicking on the select box
Step 4: Click on un-archive button on the right hand side of the screen
Your user shall be un-archived.