I just went to the Lookout Circuit, which is located next to the Horizon Rush Outpost. I won it in an upgraded S1 class 458 Italia and the Chapter Progress updated to 1/2, so you could try to replicate that step to see if you can make some progress.
I happened to have never run the Lookout Circuit - just in case this is bugged similar to other events, try a Circuit where you have not unlocked a Rookie accolade.
The English wording of chapter 4 ends with “win 2 Road Circuit Events in.” as if there is supposed to be a time requirement as with chapter 3. I got confirmation from the team that there shouldn’t be a time requirement on this chapter but you might keep an eye on it to make sure you win two circuits within a short amount of time.
Another step you might try is to not use Fast Travel between races, since Fast Travel seems to have reset the Chapter 3 progress. (I Fast Traveled to the Chihuahua Circuit for my second race and the counter did not reset).
MonoarNZ mentioned restarting, but for anyone else having trouble with Chapter 4, do try rebooting your device as the first step in troubleshooting.
I have had this problem previously and fiddling around with a different car for a while and changing back fixed it. I would also suggest making sure you change to the 458 in one of the Festival sites or a player home instead of out in the world, as other challenges (like seasonal pr stunts) have not registered for me as if I was using the wrong car until I switched in a festival site.
It worked for me on Series X. I did the Horizon Festival Circuit twice in a row and I’ve raced that track many times before so that shouldn’t matter. My guess is that OP isn’t using that exact car since there are a couple of similar versions or maybe the PI is wrong.
For TheGillesMuller and the rest of community members posting troubleshooting help requests: Nobody here is a mind reader, and anyone smart enough to think they know they’ve done everything right should also be smart enough to know that the first response to a “I need help” is going to be a question about every step already taken to try to solve the issue. If you don’t post that you’ve done it, it’s reasonable to assume you need to be asked for confirmation. We have plenty of smart people here who get blinders on once in a while and completely miss the obvious.
Reacting as if it’s an insult to go through a checklist of verification steps is the wrong attitude. It doesn’t mean the feature isn’t bugged, but we can’t know until the person asking for help provides all the available info that the helpers don’t have.
Max I post on here regularly and it’s next to every post that just on this profile alone I’ve been playing Forza for 10 years, if I’ve been playing a racing series for a decade and not knowing when I’m driving a car + what car it is, particularly the cover car of the game that I think is the best Forza will ever get then something would be incredibly wrong.
I already apologised before I said what I did because I know how it sounds but asking a Forza player if they’re sure they’re driving a car is like asking a COD player if they’re sure they’re firing a gun.
It may be the wrong attitude but I guarantee most people in the real world would feel you’re treating them like they’re stupid if you questioned them doing the most elementary thing in something they have a lot of experience in, even if they wouldn’t say it.
I was already well aware I was going to sound like a lot of words that aren’t allowed on here but that’s how I feel, I personally would assume anyone coming here pays a certain level of attention to what they do in the game that is well above not knowing when + what they’re driving.