Still no power steering after replacing the power steering pump?

The power steering suddenly went out. Managed to get the truck home and began investigating.

No leaking power steering fluid that I could see.
The reservoir was still full.
Got the front of the truck off the ground and tested PS and it was fine.
Lowered the truck back to the ground and the issue was back.

On the advice of a friend, I replaced the power steering pump. Once done, same issue as before, no power steering.

Convinced there was something other than the power steering pump was wrong, I gave up for the night.

I went out today and had son crank truck while I was watching the power steering fluid in the reservoir. Then all of a sudden, I couldn't see the fluid anymore. I checked the level, and it was right on. And magically the power steering came back on the truck.

However, the power steering fluid almost immediately turned a milky yellow color.

So, the power steering now works but the fluid is a milky color.

Is that a problem?

Any help is appreciated, thanks.