why does my transmission get too hot and then won't shift gears in my 2007 Nissan altima

When is the last time you checked the level of the fluid? when is the last time the fluid was changed ?

first of all check if you have enough transmission fluids, if that is not the culprit then the solenoid could be the one.

make sure u check if it is cvt fluid and not tranks fluid and check level and do a flush may have too much metal and have block