radiators only bleeding air, no water

Hi - i've been noticing our (hot water) radiators have been in need of bleeding (cold at the top, hot at bottom) so I went ahead and did it yesterday. I shut off the system, turned off the fill line and bled the radiators. I started on the downstairs units and they bled air to water just fine. Then I went upstairs and only got air...loads of it. Almost every radiator on the 2nd floor bled air for about 15 seconds, but water never came. I wasn't sure what was going on, so I decided to turn everything back on and see if it would refill properly.

Now that it's back on, I feel some warmth in the radiators upstairs, but they are generally pretty cold. My wife is complaining that it's freezing in the bedrooms (it is) so I need to figure out why I can't get the upstairs to bleed properly.

Did I screw up by starting downstairs? Should I drain and then refill the whole system?

I could really use some help here. Thanks, Matt

You need water flowing in, in order to push the air out. You do have a working pressure reducer feeding this system, right?

The fill line needs to be left on.

ok, fill line is open...still only getting air

So I shut off the system, left the fill line open and still only get air coming out (upstairs).

I looked at the fill line and there is a B&G reducing valve (model 110192) with a 'flip lever' on the top. It seems that water only enters the system when I flip the lever up.

Inbound water pressure is about 40 PSI, and I have a booster that takes it to 65 PSI.

Is that valve working normally?

Thanks, Matt