I have a radio receiver which operates on dry cell batteries. The battery compartment consists of two tubes one houses 3 cells while the other one has one cell. Both tubes have springs on one end (which touch the -ve pole of cells). Due to batteries being there for a long time there has been electrolyte leakage which has spilled inside the tubes and the springs have got corroded.
An emery board or light sandpaper. Clean off the residue gently by sanding the connection areas lightly and then give it a try, it necessary, try it again until the circuit is complete.
I have also used an emery board or fine sand paper. Something else I would have tried is Q tips with alcohol to clean the area.
Sanding the battery terminals ( both ends ) can help older batteries. Pencil erasers used inside the device and on batteries, can refresh contact like on remotes.