If HWH Jack's, are you sure they are really up all the way? It's common for them to not come up the last 1/4" or so. Periodic cleaning of the cylinder shafts is needed.
To get retracted for now. Extend - spray with WD40 - retract. Or. Use something to lever to jack fully retracted.
Then follow cleaning instructions. This is what HWH has to say about maintaining their jacks using WD40.
http://www.hwhcorp.com/ml47149.pdf