Are you sure your thermometer is right on? Any way, try letting it set for a while. . .
Sometimes jams need to set in the jar for a while. I have had things that I though were not going to jell, then canned them and in a couple of weeks the stuff sets up.
If you are truly desperate, you could try a small amout Clear Jell (cook type), which is great for thickening pies and great for canning pie fillings. I have an Adobe file of jam recipes using clear jell; I can send it to you if you want to check it out.
And pie filling--if you can preserve jam, you can make some pie fillings with those cherries and can 'em. You will need the cook-type Clear Jell, quart jars, BW bath. Rrecipe batches are usually about 6 quarts worth (6 smaller pie fillings), and I think I have instructions for to make just one quart, which you could try to see if you like it. I like home-canned apple pie filling.