Handbrake Failing the MOT

[Fozzy]

Put a Dturbo with gti rear beam conversion in for MOT apart from failing on smoke it also failed on handbrake (little to no effort both sides) I thought the car would be fine as before MOT i parked the car on my drive(a hill) and it held no problem i even checked individually and both wheels didn't turn.

I checked this evening and both the levers in the rear callipers turn as they should, what else should i be checking, the handbrake only goes up 4 clicks.

Thanks
John