SSD dead? "The operation couldn’t be completed. Invalid argument"

When running First Aid, you should run it first on the physical drive, then on the hidden APFS Container (it will automatically scan all volumes within that Container as well). Within Disk Utility you need to click "View" and select "Show All Devices" before the physical drives and hidden Containers appear 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 listed. If there are errors, run First Aid again until the errors are gone. If after several attempts the errors remain, then the only option is to erase the whole physical drive followed by restoring the data from a backup.

Here is an Apple article with instructions for erasing the whole physical external drive:

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

Of course, the external drive may have a hardware failure (could possibly be a cable or adapter/hub/dock issue as well). Try using another USB-C port especially on the other side of the laptop.

You can try checking the health of the external drive by using DriveDx (free trial period) and posting the complete DriveDx text report here using the "Additional Text" icon which looks like a piece of paper on the forum editing toolbar. You will need to install a special USB driver in order to attempt to access the health information on the external drive. The amount of health information on SSDs vary by type & manufacturer...some have very little health information.