We need to know about how the mechanism works.
If it won't go up, how do you know that it still goes down?
Post some pics of the mechanism.
Cheers,
Peter
It is a HappiJac brand bed lift. When I am not using my motorhome the bed is always in the up position. On this occasion the bed came down ok but would not go back up
Start pulling things apart, sometimes faults are obvious when you can see the mechanisms,
Can you hear a motor sound when it's coming down?
Is there any indication or sound when you try to raise it?
Is it a 2 way switch that raises & lowers it?
If there is a motor noise coming down tells you the motor should be o.k., if the motor runs trying to raise it you have a mechanical problem, maybe broken cables.
This is USA video. Towards the latter part of the video, it shows an electric motor that drives a number of cogs via chains and a shaft. The chains have similar links to bicycle chains. There are chains in the legs that raise and lower the bed frame.