Transcend Hard Drive - Not mounting - El Capitan

MacBook Pro (13-inch, Mid 2009)

El Capitan Version 10.11.5 (15F34)

Recently tried to connect my Transcend StoreJet Hard Drive to my laptop, but Finder can't see it. Tried to open it in Disk Utility, but it's said there the disk is not mounted. Tried verifying the disk, repairing and mounting it, but it's not working. Is there any solution to mount this disk without losing the files on it?

Thank you very much for your help!