Bama1, I have the toro version of your viking. Is this electric pto or is it manual pull lever and blades start to work.
I have manual and your belt is either wrong size (if you just changed them) or take off the hood of the mower and adjust your tension on the pull lever. fairly simple operation but check your owners manual for exact sequence to procedure.
If it is electric, Did you cross some wires recently? Did you break a wire or short a wire? If none of those are true your pto switch is probably the culprit. change it and you should be keen. If that did not work then I am affraid it is the electric pto itself which is around 175 bucks. or so. good luck.