You could have a stuck valve blocking flow, or another possibility and maybe more likely is that there is a screen on the supply side of the pump that is clogged, usually located in the supply tank, this is not the return side filter, if so equipped, as those look like a normal oil filter. A blocked screen would starve the pump causing cavatation in the pump, screaming noise and heat are the identifying pointers. You will need to drain system and remove supply hose unless you have access from a different direction. Only other thing I can think of would be a lot of water in the system, would turn oil milky white.
