2000 Passat V6 wagon -power steering

wagon won’t hold power steering fluid - could not see leak on hose along engine. what are other causes of leaks?
or fixes?

You could have a small leak out of the rack, and at highway speed a few drops here and there will not be noticeable. But cumulatively, it will mean a drop in your reservoir level.

The most common place for power steering systems to leak is the seals in the rack. They’re subject to the most physical wear and are the ones that hold the pressure in when you turn. And 11 years old is not an uncommon age for this to happen. I’d bet if you put the car on ramps and slid underneath you’d see the residue enderneath. You might even find a torn rack boot, although do not be misled…the boot itself only keeps dirt away from the seals, it isn’t designed to hold the PS fluid back.