On one of your pics, i circled what should be the outlet port on the hand pump and the filler port for the hand pump reservoir. You run a line from that outlet port on the pump to the port on the forward side at the bottom of the lift cylinder. I would set the valve selector to cab raise. This is just so any fluid on the rod end of the piston will return thru the normal return path to a reservoir As the piston moves up toward the top end while lifting the cab. I don’t think they typically have much fluid in them on that end as I think most people only pump long enough to get back over the balance point and the cab comes the rest of the way down via gravity. I don’t think the cab cylinder typically sucks much fluid as it is easy to suck in air around the rod seal as it was not designed to resist pressure in that direction. At any rate, the fluid needs a path to return from the cylinder.
top off the hand pump reservoir and you should be able to pump the cab right to the top. once there, put in a brace to insure it stays there and fix the latch. When done with the latch repair, remove the line you added and put the original hoses back on the pump and cylinder ports. With the selector still in the “cab raise” position, pump on the manual pump to test that the system doesn't leak/will hold pressure. This should open the hydraulic latch and the pump handle will become solid as the fluid has noplace to go. The pressure builds because the lift cylinder is fully extended and the latch should now be open. Now check the lines and latch for any leaks. if it is not leaking, remove the brace and select “cab lower“ and pump the cab back over the balance point like you normally would to close the cab.
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