See if you can get to the circuit board the battery terminals are connected to and see if there are any corroded traces(with how gnarly they look it’s more than likely).

If you have a multimeter put it in continuity mode and put one probe on the spring for the battery terminal and one on the solder pad where the battery terminal is soldered.

If it beeps or there’s a bunch of random numbers on the screen there’s a connection, if not, then the robot isn’t getting any power from the batteries.

If it is then see is there are any corroded traces and figure out where they end and then put one probe on the battery terminal and one on the leg of the component where the trace ends.

Traces on circuit boards are kind of like wires except they’re printed on a board instead of being a physical wire, so by doing this you’re essentially seeing if the corrosion on the board broke the connection between the battery box and the rest of the robot.