When was the last time the Hy-Tran and Filter were changed. If the fluid is ancient, it might be so full of “moisture globs” it has filled and plugged the filter.
I’d pull the rear cover and take a look at the fluid, if it’s completely nasty, I would goto TSC, Farm and Fleet, Rural King, etc, pick up a cheep jug of “hyTran equivalent and a filter, even a cheep, it fits but not right Fram would work for this. If I it’s full of sludge, drain and clean out the case. Put on the cheep filter and fill it with the cheep fluid. See if operation is restored. If it then works. I would run it for a couple minutes to help flush everything out. Then drain the cheep fluid, remove the cheep filter. Refill and replace with the proper fluid and filter.
if it didn’t work, then you didn’t use the expensive stuff only to find out it didn’t do anything.
This is just how I would do it. Others may have other ideas.