didn't realize it was PB. crack a bleeder & if that frees it then close the bleeder & pump it up & undo the MC to booster bolts & pull the MC forward a bit & see if that frees it. If so take the bolts the rest of the way off & pull the MC forward so you can get at the rounded pushrod threaded nub & shorten it till you have a slight bit of clearance between the round nub and the bottom of the piston recess "thimble" in the back of the MC