Can’t mount external drive - Mojave came up here after a lot of looking around. Even seen a couple of examples of my issue,  JT not sure what to do. Have tried a bunch of stuff and still cannot not get drive to mount. Apple says to wait for a call back in a week after the holidays. Doubt that anyone is reading here now, but.....  tying anyway. Older HP external drive and recently upgraded to Mojave. Here is some of the details I posted on Apple ———-

https://discussions.apple.com/thread/2

Not on the actual computer now but for the life of me can’t figure it out. Any ideas - all my back files are there. Tks Stumped. 

Edit add info:

High Sierra previous os. run in safe mode, empty caches, remove .plist for time machine, try on another Mac, run iboysoft recovery software. cannot unmount as it won't mount. HP5000s drive. Drive just spins and spins showing activity but won't mount. connected by usb to MBP w/ Mojave. Tks! – Stumped 6 mins ago
From Terminal, what happens if you try:

sudo diskutil repairVolume disk2s2
sudo diskutil mount disk2s2


This will run the Disk Utility disk repair process. Can you report back with any errors or output you get.

You can also try booting into Single User Mode (at start-up hold down Command-S). That'll drop you into a command-prompt and you can try

sudo fsck_hfs -fy /dev/disk2s2
shutdown -r now


That runs a filesystem check (hence fsck), and can also repair damage, then reboots. After the reboot, check and see if it mounts.