Can't upload my addon?

I’m trying to upload a spawn protection addon as an expansion to my Evolve 2014 addon. I only have 2 workshop addons for gmod in total, with about 80% positive ratings. I’m getting an error code (25), which means that I’m hitting some kind of addon limit. Why am I being limited to two addons? Is it because my addon is a single lua file, or what? The GMA is good and verified.