I have not had this problem with the Ryobi Router, I have had plenty of tools stuck after extended periods of non-use. I expect that some of the sugars in the sawdust have absorbed moisture over time & have glued the mofing parts together. Either that or corrosion has set in.
The first thing I would try is to spritz liberally with WD-40, let it sit for an hour or so. & if it has not freed up, repeat a few times.
Spritz into every possible opening you can find in the lower part of unit. about all you can do to it is make it operate smoother.