new holland tn65s doesn't go into gear?

i have a New holland TN65s that seems when it has been working for a while cutting hay or whatver when you stop take out of gear won't go back into gear or i should say it goes into gear by feel but won't engage forward or backword i beleive it is heat related because after letting it sit for a while will engage and and you can go on and work did this maybe 5 7 times over the last week i believe the error code is 56