DKRed never can identify my outline layer

I’ve tried DKRed several times over several months. Each time, I include an outline layer (M1 for Altium), but renamed to either .gko, .outline, .profile or all of them and it can never find the outline layer, so cannot process the files as DKRed. What is the secret here?

Hello @Dan_Rhodes,

What design software are you using to produce your Gerbers?

I am using Altium