Unable to fix Samsung external SSD mounting errors

We can and see if the Mac will see it through the systems information. Apple menu About this Mac. Click on system report or more info button. Scroll down to the USB option in the Hardware section. If it's there, Apple sees it but you don't have access to that drive

How old is the computer and the external drive separately? According to your original post, the last successful back up was months ago? One other question, what was the format of the external drive when the back ups did work? That's important to know

Oh. The questions I was asking you is after the external drive is discoverable but cannot be accessible. Lets backtrack. One thing to try go to Finder then preferences click on the tab labeled sidebar on the top menu bar. scroll a little bit. Select the option External disks under locations to list your external drives in the finder side bar. It may have been checked off. Make sure its checked on.

Additional information to look over. If the option to have external disks in locations is checked off, then go to the generals tab on the same top menu bar. This will ask you to show items on the desktop. One of these items is external drives. Make sure this option is selected or checked as on as well.

Go through your finder settings and see if the settings are on. If your settings match the settings marked down in a red box, then you can try going through safe mode

Try a different port

I was meaning by providing the steps is to see if the 2 options were turned off. If there were then the external drive wouldn’t show up. Were the 2 options turned off? I’ll try to add photos