Massey 88 no power steering

[Claym]

Hello I have a Massey 88 that I have
Rebuilt but have not been able to get
Power steering to work. I did pull the
Pump and clean the inlet screen
And pulled the steering filter and
Cleaned it but did not help. Fluid has
Been changed . If anyone has any
Suggestions as to what I can do next
Would be greatly appreciated. Thank you