Only 1 out of 7 baseboard have heat coming out
You may have an air lock.  Any air in the system will keep the water from flowing. Your system and BB's should have little air vents to vent the air.  Investigate these air vents (sometimes called "bleeder valves") and what they look like on-line and then start looking.  Under your hinged end covers you should find these mini air vents. They usually take a flat blade screw driver to open.  Turn the top slightly to the left.  It should spit and sputter air and water.  Once the air is gone and you only have water coming out close the vent and go to the next one.  Once all of the air is out of the system, the water will move and bring heat to the area. (Look up air vents for hydronic heat systems, sometimes called key vents.) Also turn up the water pressure on you system.  It should be around 10 to 12 psi.  You have to have some water pressure in the system to drive the air out.