If it turns on when plugged in try hitting the off/stop button after plugging it in. If it is an analog knob make sure it is in the off position before plugging in.
Please provide the code off of your old belt and I'll see if I have that size in my stock. The code will look something like this:STS 60 S3M523 When you have that number visit me at my website breadmachineshelp.com I help people with belts and belt installation very frequently! thanks, Daryl