During the upload process, users that have the permission to upload assets as Pending Approval can select an Admin user to approve their request:
The approver selected will receive an email notifying them of these newly uploaded assets awaiting approval.
When the approver nivgates to the Approve tab and notices the assets are now missing one of the following could have occurred:
1. Assets have already been approved by another Approver
Another user with "Approver" permissions has already approved gone into the Approve tab and done a bulk approval of these assets.
2. Assets have already been approved from the browse/search screen
Another user with "Approver" permissions was browsing or searching for assets and noticed the Pending approval status of these assets and approved them from, bypassing the Approve tab entirely.