I have recently been banned due to the use of game add-ons within zombies.
I thought it was going to be okay to use them offline / custom games, however that was proved wrong instantaneously.
Would there be any way to resolve this?
No worries if there isn't, thank you.
No way to resolve that, read the anticheat policy https://forum.plutonium.pw/topic/3449/anticheat-ban-policy.