I don't know what updated a couple days ago, but since my localhost:32400/web had a makeover, PlexConnect is not discovering my PMS (same network, diff machine) and also it cannot sign into MyPlex.
PlexConnect does show when I open Trailers, but I cannot sign into MyPlex and it does not discover my PMS machine either, using both wifi and ethernet.
GDM = auto discovery of Plex devices (Plex Inc's version of bonjour if you like).
If it fails it will fall back to the hard coded IP but most users should not need to do this unless they have disabled GDM on their PMS or they are blocking it on their router/firewall