This page helps you get ACC working reliably with RaceLab overlays. The two key requirements are: disable fullscreen (so overlays can draw on top) and enable ACC telemetry via broadcasting.json.
This is the most accurate source if ACC updates change behaviour.
RaceLab overlays require the game not to be in exclusive fullscreen.[2]
OneDrive users: if Documents is synced, the file may be under your OneDrive Documents folder instead.[1]
Open broadcasting.json in a text editor and set it to:
After saving, restart ACC. If you edited this while ACC was running, exit the game and also restart RaceLab to apply changes.[1]
Where to go next:
Unofficial RaceLab support site maintained by Scottozy. Information is provided in good faith based on official documentation and community experience and may change as RaceLab is updated.