Tape won't spin. Please help!

I purchased this Walkman off of eBay recently, and in the description it claimed that the Walkman wouldn't work with batteries, but instead would work while plugged in. When I received it, I tried batteries and the indicator light turned on and it sounds like the belt is spinning inside of it but the tape that I'm using (good condition) isn't playing. I noticed the little nubs inside of it aren't rotating. The belt itself is something I looked at and it looks a tiny bit stretched so I ordered some new ones and they arrive tomorrow, but I was curious if it isn't the belt at all and instead is another problem. Can anyone help? This is my first time doing this sort of thing and I was super excited about trying a Walkman out for the first time.