Venting floor heating
Your hydronic floor heating system could have several problems.  You'll want to troubleshoot to narrow it down:

If you hold the pipe that returns from the upstairs room, is it warm like the other pipe?  If so, then there is circulation happening.  In that case, you can try to balance the system by directing more flow into that pipe.  This is done by turning those adjustment valves on top of the return manifold.  You would turn them down for the other rooms, and turn the up for the colder room.  If this still doesn't help, then you could add insulation to the upstairs rooms.  If nothing else, maybe your upstairs subfloor is more thick or more insulating that the downstairs rooms which are working.  You could try insulating from below with reflective shielding to direct all the heat up, but this would be possible only if you still had access to the underside of the subfloor.

There should be no air in the pipe, because that will prevent circulation or make the pump inefficient or damaged.  Air should be completely flushed from the system by bleeding one line at a time with the pump on.  If you grab the return pipe from upstairs and you feel no heat while the system is running, then you could have a lot of air, or perhaps a kink in the line, because there is no circulation coming through it.