Try to remain calm and walk through the steps below. In these cases, you may get bumped out of the assessment temporarily. When LockDown Browser appears to 'freeze' or closes, it is commonly due to a pop-up from another application appearing behind the LockDown Browser (meaning it will be hidden from you), clicking a corrupted web link (which LockDown Browser will block), or losing your Internet connection.
Troubleshoot access to a LockDown Browser assessment in Canvas