First thing ,snapshot manager may not show the available snapshots always, it just displays the content of vmsd file if the file is empty it will not show details in snapshot manager.
Coming back to the issue
1. Check if this is a repeated issue, since the snapshot manager is empty, I feel the backup software initiates the consolidate command and it fails.
2. We have to check the logs why the consolidation is failing, and generally the if any failure occurs , backup software should retry 10 iterations to consolidate again.
There are multiple contributing factors for snapshot consolidation issues, we have to check the logs and determine the actual cause of the issue.
Try to consoldiate the snapshot and post the error message (error screenshot, vmware log, hostd log) or open a case with VMware to find the cause.