First, check which role you are in which you should be able to see in the top right-hand corner of the worksheet tab.
If you are in the Editor role and the lock option is unavailable this means you are in an open request round.
Assign yourself or other editors the accounts that you need to lock. From the contributor role, you can lock accounts. Then you can submit those changes to be included in the approval process.
Have more questions or need assistance?
Submit a Request