super hard clutch pedal

My question for you is- was this all in before the storage - if so... what changed during storage. Honestly rust on the hydraulic bores or a leak / air bound check valve is all that could go wrong from sitting.
I don’t know that particular system personally but a hydraulic clutch release set are all pretty much built the same way.
Maybe rusted throw out bearing collar?

If new set up- different question.