I would change the USB cable and make sure that the hard disk is spinning whnr I plug it in. If it dows not speen you have a possible hard disk failliur. Mean you external boitier is defect or the hard drive is defect.
if it is spinning change the usb cable and try it again. it that does not work open the boitier and put the harde drive in the machine internaly you will have a final state of the disk. if the disk is good change the boitier or send it back to the manufacturer for defect.
If the above said all are fine- then final option would be installing the WD driver on the machine and try it
You mentioned that you have already tried your external hard disk to another computer unit and it didn’t work. It is very obvious that there might be a hardware problem with your external device. You should try your device on another computer for the last time to make sure of the problem.