stearing and 3 point hookup wont work?

why internal hydro. pump is not sending enough or any fluid up to main pump?I have chased the problem back to a time the tractor stopped pulling and had to be shut down to put more fluid in. Upon checking fluid level the 4440 was showingt below full line.
44440, 7300 hrs not well maintained but maintained.I added fluid to radiator cooler part and 3 pt worked unntil it ran out,
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