Hatchback lock cylinder

A 1997 geo metro hatchback. I applied chassis grease to my hatchback door lock latch mechanism. It opened and operated fine during warmer weather, now that its almost freezing outside, i cant get the key to release the latch. How do you open a faulty hatchback door? If io ever get it open again ill flush all the heavy grease off, and use plain old motor oil. thanks to any "body men" out there for any advise.

reach in from back seat and push down on lever on left side of latch

reach in from back seat and push down on lever on left side of latch

YES! that worked great crvett69. Thanks for your knowledge and help.