It was working fine, just switched the loads and now just a buzzing noise when I turn the start button

Your detergent door may not be closed all the way... or your hot cold valve may need to be replaced!

It's possible it's the belt.

I just had the same or a similar problem. When pushing the start button, it would buzz as if it were trying to start but it could not. I took the dryer apart and pushed the button again with the drum removed. There were some crunching noises from the motor as something came dislodged. After that the motor was squealing in an unappealing way. A few drops of oil on the drive shaft cleared that up and now it works fine. Hooray!