Swisher 44" blades won't engage

I just had this mower serviced 2 weeks ago. Started to mow acreage in upstate NY. Took down lots of 1-2" wild rose bushes up to 6' high. Everything going great until I noticed after mowing about 2 hours that the grass wasn't being cut. I took it apart and saw the belt had slipped off of the pulleys. I put the belt back on and started to mow again. The blades still wouldn't engage! It was so hot out and I didn't have the energy to take it all apart again. Do you think I should just replace the belt? I did some research and saw that other people seemed to have this problem also. Someone suggested a Kevlar belt for less issues. I also saw that some people had problems with the blades freezing up. How do I prevent this from happening? What do you all think? It's too hard to load the Swisher onto my 5' x 10' trailer again. Such low clearance that it keeps getting held up on ramp. Only got it on by putting moving dollies under it.
Any ideas are greatly appreciated! Thanks!