PTO failure, very low hydraulic fluid level, bad hydro pump off the top of my head. Is it electric or manual PTO? Our electric can be finicky. Sometimes it will "click" on, but there's no hydraulic function. We disengage, wait a few minutes, reengage and all is good. Possibly a temperature issue, as when it acts up it's almost always after a long highway drive.
P.S. Might be better off posting in the "Rubber Hits the Road" section. More people will see it there.
Start at the beginning of the system and see what, if any of the system is working. You should be able to tell if the PTO is engaging and then see if there's any movement in the hoses when there's a demand for hydraulics. You should see the hoses surge a little with the movement of pressure. Most likely with it being outrigger and boom it is one of the items listed above, unless it's a problem with the outrigger and there's a safety on it preventing the boom from working while the outrigger is up.