The clutch on my 2008 Nissan Versa Hatchback does not have any resistance when pushed. The car does start but I can't get it in gear. There were no problems the last time I drove it. There was no hard shifting, grinding of gears or anything indicating an upcoming problem. Where should I start looking for the issue? Linkage all seem to be connected.

Hydraulic? Fluid in resivoir? Pedal not come back up?

Yes it's hydraulic. Where is the reservoir? Do I have to remove the air box to access it?