Buy some #0000 steel wool. Use isopropyl alcohol as your libricant and scrub the build plate. Youre not looking to remove anything but the sheen. I have 12 P1S and had 8 prusa MK3S+, and this had to be done to all of them. Sure, out of the box the prints stick just fine, but then prints will fail to stick. This was always my solution, which I picked up from another forum (Prusa). It doesnt ruin your build plate at all, doesnt even really change how it looks. Just knock the sheen off of it and youll be good to go.