Played through the campaign on my third character and the I don't have the flashpoint milestone. Did Caydes patrol and heroic event quest for it but still hasn't shown up. Done the base game and both dlcs and just can't get this milestone. Other characters are fine. Seen people having this problem from months ago sad to see still no fix. Bungie please address this.
Cayde has gone to the Reef so couldnt give you the milestone. Wait until he gets back...
The flash point is mars. You have to unlock the planet if you’ve not done it already.