I can open my Catalog on my laptop and when I move the external drive to my desktop it asks for me to test its integrity before opening. It will start the process but in the middle of testing it stops and won't even try to open. I'm please help. I am not sure if it is a computer issue since it opens on my laptop. I do have a backup if I can use that.
Try copying the Catalog from the external hard-drive to desktop and then try to open the Catalog. Check if you are able to open the catalog from there.