you sure the truck is not in lift interrupe if the battery is weak or very low it will not allow you to lift l would look at that first try to charge the battery and than see if it lifts you might be chasing a problem that is not there. If that does not fix it try look at the hyd contactor see if you can manually push it in to see if the hyd motor turns on it is possible you have a bad motor
You also could put a meter on the two cables at the motor and pull the hyd handle to lift and see if you have battery voltage to the motor. Also check the switches that you talk about in your post that is what signals the contactor to close make sure that when you pull the hyd handle that the switch is closing l seen them come out of adjustment and not close. Hope l was of some help.