No Sound Coming out of Subwoofer

I recently got gifted a used JBL ES250P for free. I was told it was functional when it was last used; however, I have been unable to get sound out of it. Some of my basic troubleshooting and observations are below:

The light is on and I hear a quiet low buzz when a cable is plugged into the RCA inputs.

It is hooked up to my computer via the line out into an auxiliary splitter, with one output going to my monitors and the other output going to the sub.

The cable works, as I have tested it on my monitors.

Sound is coming out of my monitors (also hooked up to the splitter)

The phase is set to 0°, and the input is set to normal. The crossover is set to 50 Hz, the level on the sub is halfway up, and the volume on my Windows 11 desktop PC is around 50.

I have attempted switching the outputs on the splitter around, and I have attempted switching the RCA cables plugged into the subwoofer input.

The RCA connectors on the subwoofer seem to move around when I plug the cables in, so maybe those don't work?

I have currently tried switching cables and using it without the splitter with no luck.

I have attempted to plug the subwoofer into the headphone output on my audio interface, and there was still no sound.

When the subwoofer was loaded into my car, it was set down so that the knobs were facing down. It doesn't look like there was any damage to the knobs, but I wonder if that could have damaged the potentiometers.

Thank you for your help! If you need any questions answered, let me know.