Hello and Welcome to LMF, from another Kansan....
Check your belt path, you may have missed an idler pulley along the way...
Usually when a belt comes off, there is a reason... check to see that all pulleys & idlers turn freely and that all are in line... also check for missing or bent belt guides/guards..
If you don't find the problem, post back with the model # and someone may have an exact place to look... :smile:KennyV