The issue was as simple as an expired certificate. Generated a new one and it solved the problem.
Within the last week, the control station has had the disconnected icon in Navisphere (CS is currently running Unisphere). I have manually restarted both SPA and SPB, which removed the disconnected status, but I am still unable to access Unisphere on the host IP. The status in Navisphere is "Host Agent not reachable" and showing "Inaccessible" as the connection state. I've also connected to the NS20 via serial to verify settings and it appears that the config is fine, including the NTP settings.  I'm kind of stuck at this point.
NS20 - Control Station connection state "Inaccessible"