Sounds like the item you are trying to open is an Alias to the original data which has since been deleted or moved. This is common if you transfer items to external media which will break any Aliases you may have created on the original drive.
Or maybe the file system has been corrupted. Try running Disk Utility First Aid on the hidden Container. Within Disk Utility you may need to click "View" and select "Show All Devices" before the hidden Container appears on the left pane of Disk Utility. Even if the First Aid summary says everything is "Ok", click "Show Details" and scroll back through the report to see if any unfixed errors are listed. If so, then run First Aid again until there are no more errors. If after several attempts the errors remain, then you may need to run First Aid while booted into Recovery Mode (assuming the data is on the internal SSD).