I posted this in far down another thread, but I figured this would reach more people.
If you are 152 and haven’t received watchdog, these are the steps I took to get mine. Hopefully it helps.
Sign in to Halo Waypoint here:
https://www.halowaypoint.com/
Click your profile and select “Drops & Code Redemption”
After that, there should be a “history” tab. Look at that and then launch the game whenever.
This is what worked for me at least.
If that doesn’t work, launch halo 5 again and swap an armor piece or something and then try halo Infinite again.