Excellent that you got it working again. If it acts up again, consider that Passports have been rather troublesome here historically. As they age they seem to demand more power to turn the platter motor. Eventually they demand more power that a single USB port can deliver.
"Name-brand" external drives seem designed to go on sale every other weekend. My best recommendation is to replace with drives that are better engineered. After fighting "name-brand' for for several years, I now use now use only the OWC line of externals based on recommendations from even more senior contributors here. From my desk chair I can see five trouble-free OWC drive serving three Macs. Yes, they cost more, but that issue pales when I ask myself, " What is my data worth?"
However, I am fully aware that not everyone can afford to toss out the cheap ones and restock with pro models in one fell swoop. There are some workabouts that seem to help improve the Passports' ability to continue working:
1) Formatting: WD drives including Passports usually come formatted for Windows. Even those sold as "for Mac" have odd partition mapping and formatting schemes. If the drive does NOT have to be shared with a Windows computer, erasing and reformatting the drive with Disk Utility often make it more responsive. Select "GUID Partition Map" and, if the external has a mechanical drive, "Mac Extended (HFS+)" for the format.
2) Power: as a big part of the problem is the demand for power, you can boost the power going to the drive by getting a POWERED USB hub (comes with its own independent power supply) and placing it between the drive and the computer. That takes the power demands off the computer's USB ports.
