forgive me for stating the obvious but, if you have cavitation in the tank the hydraulic motor must be turning to create flow in order to make cavitation. you would actually hear the motor running. The contactor would pull in (with an audible click), then the motor would start running immediately with an audible sound.

But before you do ANY of that check your battery voltage, make sure the battery is fully charged before any testing. Does this have an industrial battery? or is it a battery pack? Check the fluid, make sure it is over the top of the cell plates if you have access to the cells. If the battery is discharged it cannot supply enough voltage to make the motor run correctly.
24v system? you should be reading on a vom at least 25.5v or more for the motor to turn fast enough and have the power to run the hydraulic system.
Even a dead/discharged battery should run the motor slowly, it just may not have the power to do much under a load. But if the motor is really not turning then those batteries are more than likely dead.

(IF the battery checks out ok) what i would check is the relief valve, if that is stuck open, pressure spring broken the fluid would just bypass back to tank.