kyleniels, I'm also using the Activity Analog watch face (but with Subdials) and I'm experiencing the same issue. The black bar goes away when I swipe to another watch face and back (but it returns). This issue started for me after updating to watchOS 7.0.2; another issue that started at the same time is the Always On Display will sometimes go dark. After I 'flick' my wrist, the display lights up, and goes dark again (similar to covering the light sensor on an iPhone). Tapping the display seems to stop the issue. Do you have this issue as well?
I've already submitted a bug report at Apple Feedback and chatted with an advisor. The advisor suggested restarting the watch (I did that, but cannot tell if that resolves the issue because the black bar already went away while switching watch faces). The advisor also suggested unpairing and repairing the watch to the phone (have you done this)?