Steps for this glitch-
1. Go into player growth menu- Make sure you have a GK build in any playstyle (Just put it where i did) Have a playstyle you want to use this glitch on.
2. Set the GK playstyle as default by pressing square on ps4 or X for Xbox
3. Open edit player whilst you have your GK playstyle as default and apply the helmet and pants and then back out.
4. Open player growth menu once again and select the playstyle you want the glitch to be on as default playstyle.
5. THIS STEP IS MOST IMPORTANT- disconnect your internet and connect it back straight away and go onto the game(To disconect on ps4 go to network settings and then uhtick the box and tick it again)
6. After you have connected back and returned to the game accept the message and go back into pro clubs.
7. open player growth menu and set the build you want the glitch to be on as default playstyle and when you load into a game the glitch should have worked.