If you run a newer version of Spine, your hotkeys file will contain hotkeys for that version. If you then change to an older version, it may have hotkeys that the old version doesn't recognize. If you delete your hotkeys file, then run the older version, you'll have only the hotkeys for that older version. That should work! You can read the hotkeys.txt
file to see what hotkeys the older version has.
If you are still having trouble, check your spine.log file for any errors or clues.