Experimenting and lost some External Disc Drive Connection…Why?

Thanks for any suggestions.
I am trying a new SD card flashed with latest LibreELEC.
All went well and it is running.
But several external drives in different bays are not showing up.  They show they were mounted and now dismounted when I shut them down, but they don’t show up in file manager.  Some missing ones are 500 Gb up to 4 TB external.
Putting the original SD back in returns set up to normal.