Try Creating Missing Folder if Missing
I purchased Affinity software many years ago and installed it on an older Mac Book. I wanted to install it on a newer device, but I had to sign in first. I couldn't sign in because I never registered my purchase/product. I fired up my old Mac where it's installed, and I received the same error messages in this thread--Hello. My old Mac runs High Sierra and can't be updated any further than that. For me, the "Affinity Photo" folder, where this thread says to copy the file "afreg.cfg" (where in other cases the file might need to be copied to "Affinity Publisher," "Affinity Designer," etc.), didn't exist--so, I created the folder "Affinity Photo", then I copied the "afreg.cfg" to it. I started my Affinity Photo software, tried to register, and this time it worked!
I see missing folders in some of these previous posts too, and hope that this might help someone in the future.