G,day Doug, Welcome, not a lot to go on but it sounds like the system is running out of oil. Its worth worth checking out the safety devices which normally apply the brakes and prevent the loader from operating when you are not in the seat. They may be defective and are preventing operation.
Then I'd replace the hydraulic filter, it could be well blocked or the wrong type. After that, and if you have a manual it helps but there is normally a strainer on the hydraulic pick up in the hydraulic tank. Pull that out and replace the cartridge or clean it depending on what type it is.
After that I'd give her a good degreasing and cleanup then call your local NH/Case or even Deere dealer and get them to test the hydraulic pump output. May as well start at the start.
Good Luck, I'm no NH expert but I'm sure there is others here who can be more helpful.