TC Not Recognizing a Compatible Extension

[Alky]

I'm playing a game (American Truck Simulator) that uses an .scs file extension which in reality substitutes for a .zip extension. They are interchangeable for the purposes of the game.
TC got slightly corrupted and I deleted the wincmd.ini file and proceeded to start a fresh configuration. Before this I could pack and unpack, view both file formats without issue. I've been through the configuration a dozen times and don't see the problem. Ive done the "associate with" option, but no luck, I get an access denied error when trying to get into the .scs file.
Anyone know off hand what I'm overlooking?
Thanks.

[Gral]

No need for any associate - just press CTRL+PgDown on .scs file to open as zip, or Enter if system-wide association for this extension not exist.

[Alky]

Thank you, CTRL+PgDow works to open the .scs files. I'm not able to create an association with it though. It would be nice to be able to treat the .scs file the same as a .zip file, that's how it worked before. I'm getting an icon that shows the blue floppy disk but with a yellow! in the middle of it.