Remember that there are two hollow dowels that locate the plate against the gearbox housing, so the plate cannot move sideways. The dowels are tight, which adds to the difficulty. The plate must pull straight away from the case by repeated jiggling after the bond line is released. Heat may help soften whatever is holding it.
BTW, it is best if you can be certain that the bike is in either neutral or 1st before removing the plate. If you choose neutral, mark the cam wheel alignment at adjacent teeth. There's already marks for first gear.