I'm having issues with nameplates getting turned off every time I leave combat. (Have to manually turn it on by pressing V again)
Doesn't affect other players or NPC's, but it affects my pet.
No automation on either Enemy or Friendly nameplates.

Before Combat:

During Combat:

After Combat:

After pressing V:

The only thing that would do that is the Nameplate automation. Make sure it isn't enabled by changing to something and then changing it back to No Automation.

Edit: I would also check if there's some other addon doing it or even if it still happens when you have no addons on, incase there's some weird keybind situation.

Leatrix Plus was interfering.