Step 1: Click on the Users menu.
Step 2: Click All Users tab (top of the screen, under your school's name).

Step 3: Under status, change to archived.

Step 4: Enter the details in the dialogue box to search the staff member.
Step 5: Select the person you wish to unarchive by clicking on the select box.

Step 6: Click on Unarchive button on the right-hand side of the screen.

Your teacher will be unarchived and able to log on successfully.