My 1994 Geo Metro 1.0 L Hatchback has stopped warning me when
I leave the headlights on and turn off the ignition.
Any ideas ?

check your door switches, they seem to be a nasty culprit in a lot of prblems .... door locks not automatically locking, ignition buzz not buzzing, interior dome light not lighting, ... you get the picture?! They are in the body under a black rubber boot.