I don't think you can have both PLR and CP huds, the "team_train_watcher"s (which are required to move the carts) hide the CP hud.
The control points do still work, but the lack of visual feedback is really annoying.
You can do the visuals yourself by using the "trigger_capture_area" outputs to do fancy stuff, but there's a better way:
I'd suggest just using the PLR race hud, the carts' rollback mechanic, and onPass output of the "path_track"s to simulate a capture area on the hud.
This does require moving around the carts' "trigger_capture_area" since only one works at a time (I'm not too sure about this tho), so you should get familiar with the SetParentAttachment trick to teleport stuff around the map*.
*(my go to prop is the madmilk rotated "-90 270 0" with the "drink_spray" attachment, it is the only attachment I found that is exactly at the origin of the prop).