I've never heard of a hydraulic clutch becoming solid, so I suggest some diagnostic tests to find out where the problem is.
[1] Open the bleed valve and push the pedal. If it goes down then the master cylinder is probably OK. If it does not you have found the problem.
[2] Close the bleed valve, top up the reservoir, then disconnect the push rod from the slave cylinder. Push the pedal again. If it goes down then the slave cylinder is probably OK. If it does not you have found the problem.
[3] If 1 and 2 are OK the problem must be the clutch itself, and it will have to be removed for examination.