If your machine is not broken, it most likely is seized due to old oil that has hardened. How long since its last service? Refrain from trying to run the machine until the issue is resolved as it could damage the motor. or more...
Wheel on right side that controls the needle up and down is very tight...
If you have installed a brand new needle and still experience the problem, take your machine for service. The needle striking may further damage the machine and could cause you injury.
It's on the machine bed to the left of the wheel, flush with the flat sewing area. It probably starts with fr and then numbers. It's right below the bobbin winder.
My white treadle is hard to pull up sometimes. There is a cable that lets the top of cabinet down or open. See (from underneath) if the cable is hung up on something. Here are two websites that can help you too.
http://www.ismacs.net
and
http://sewmachinerepair.com
Both of these are very good.
I have an old white with the treadle and there is a very good website that you should be able to find out. There are two good websites,
http://www.ismacs.net
and
http://sewmachinerepair.com
you find links to more info as well.