Why did I get VAC banned when I got my GMT trophies?

[AshGe]

If you want to appeal your ban, do it through private messages as stated by MacDGuy

How To Appeal Bans

Before you send a ban appeal… If you make your ban appeal public we will automatically reject your ban appeal and hide it from the public. Ban appeals are not a guarantee. We issue bans based on evidence. Ban appeals can take up to a week or longer to be handled. If you have been VAC banned: We cannot remove the ban. We do not manage VAC. Do not send us a ban appeal about it. Do not send ban appeals to our Discord support tickets. You should only …

Now maybe your ban is simply an error, but I would still contact MacDGuy, Caboose700 or Noodleneck to get further information about it.