The pin on a single piston sliding front calliper? It has one top and bottom? It " should" just need un doing with the allen key till it is totally free then a wee tap with a long punch or screw driver and out it pops.

Daft question, but have made sure it is full loosened from the threads?

Once u only have one in (cos it sounds like u have removed the other one) u can pivot the calliper and pad cradle and work it loose?

RW