First make sure that you and your friends use the same AllDrive Setting, then if you haven't completed both tutorials Racer/Cop, please try to complete them. [suggested by GOLD-G_WOLF]
You can also try this workaround provided by another player:
batomeister24 wrote:
Guys here's a possible Solution
First off I couldn't see my PSN friend in "ALL DRIVE\FRIENDS" menu in the game for boosting so we both changed our Matchmaking Setting to Friends Game and then we both restarted our PS4's.
After that I could see the other player as a friend in the game but they couldn't see me.
Here is what we did so that the other player could see me:
1. I joined their Friends Game
2. While still in the game the other player deleted me as a psn friend
3. I waited a few minutes and then sent them a friends request and they accepted
4. After a few minutes we could both see each other under FRIENDS and were able to boost the trophies together
If this doesn't work straight away then both players restart their PS4's again and hopefully it will work.
I just did this with two different players who couldn't see me in friends and it worked.
