By "repair apps" I assume you mean apps you can purchase and download. Such as TechTool Pro, Disk Warrior, etc.
Yes, sometimes those apps can work, but if you cannot even see the drive in Apple's Disk Utility, the chances of one of those third party apps working is low. They have to be able to detect the device to try to repair it.
Can you see the device in About This Mac, System Report, if you look at the ports, does it detect and show the device?
Have you tried different ports and cables on your Mac?
Do you have access to another Mac to see if it can see the device?