External hard drive will not mount

I have a WD MyPassport external drive. I use it to save my photos/videos from first iPhoto and then Photos. I plug it into a white usb-lightning adaptor and into my MacBook Pro. I am running 10.15.4. It has always worked, but today when I plugged it in (and tried also with a different Mac), the hard drive did not mount on the desktop. However, the external drive's light comes on and flashes then goes solid like it normally does when I plug it into the laptop and I hear the disk moving.

I checked and verified that the Finder preferences was set them to show the external drive in the sidebar and the desktop. I opened disk utility and the drive did not appear. I checked /Volumes and it was not there either (in Terminal). I then restarted the computer. Still not mounting. I reset the PRAM. Still not mounting. Rest the SMC. I did first aid from disk utility on the main disk for the laptop. For a brief moment the external disk showed up in disk utility as greyed out. I tried to do first aid on it but it failed and then disappeared again.

What should I try next?