If you bled out the air and didn’t manually refill the system you may not have enough pressure to allow proper circulation.
When a boiler system is filled Via automatic feeder Normally set 12-15 PSI this does not allow for making a positive pressure on the upper floors.
You see even 15 PSI would only let the system fill to a height of 34.65 ft Above the fill pressure.
What most of us heating folks do is increase the pressure another 4 or 5 PSI so we have positive pressure above the highest radiator/baseboard so air is forced out when we bleed these types of heating systems and no chance of causing a slight vacuum when the water cools down.
Have a LMP show you how to add this pressure safely and possibly install high quality Spirovent automatic bleeders that remove micro bubbles from this system.
At least you didnt ask a stock clerk “how to” like Dumbell Jack does.
They wrote a book a long time ago about “the house jack built” LOL