I'm on my fourth week of Superdrol/Phera-Plex/Mega-Zol. I'm on low carb and haven't gained a pound nor has my stength gone up at all.
Not pointing fingers but I think far too many people expect muscle gains in a deficit just b/c they are on powerful anabolics. For me it essentially never works that way.
The only time I have managed to make it work was when I was at a very low bodyweight and without hardly any muscle mass. Even then it took the supercompensation from refeeds to yield measurable muscle gains as ubi alluded to.
If you have been on 4 weeks of SD and haven't gained muscle, your calories are too low, period. Even with 2g/lb in protein and low carbs you'd probably still get enough insulin to bulid something if calories were high enough.
In a deficit I wouldnt' expect it.
Steroids are fantastic at preserving muscle. Unless you are dealing with a particularly wet compound (and thus have trouble losing fat due to too much estrogen etc), darn near anything will work on a cut to preserve muscle. Usually people use way more than needed to preserve lean tissue. But even veritably huge amounts won't yield muscle gains for many sans calories. Food and genetics make up most of the picture.
Sure you can typically gain weight at lower calories on Testosterone than off Testoserone, but I still wouldn't expect anything from a deficit.