Debby those are very good suggestions, so many times one forgets to do the most simple things to resolve a problem.
But it seems like catscradle is having a Flow problem, the upstairs vents are closed, yet the heat is not being flowed to the first floor.
BTW, welcome Catscradle !
Is there a Damper in the line somewhere ?
Could it have been close to the first floor at some point.
I'm just guessing here, but with the registers closed to the second floor, you should be getting a LOT of air out of the ducts. Those things are usually in the Attic.
Check the Filters too, they may not be letting very much air through them.
Have a good Day !
S.W.