It’s been a while since I stopped playing Forza 7, but now when I get back I can no longer access several services within the game, for example the “special vendor” and especially the multiplayer mode. A message always appears saying that it was not possible to connect to Forza Motorsport servers.
Try just playing Freeplay about until the game gets warmed up. I think they installed some bad tubes(used to use transistors, but hey, let’s go backwards).
Or you can try going offline/online(network settings) while in the game. That generally gets it kick started.