My first login of the weeks was a few hours ago (confirmed by posts and guild seals).
First thing I did was Guild Wars which give PvP points which showed I was tier 1, I should have reach around tier 11 after 8 won battles. I didn’t receive any rewards.
While I was writing the above I decided to play actual PvP to confirm error was also there, and then I was back to tier 15 and got reward from for reaching tier 14. So now it is a question of missing PvP points for GW fights, rather than missing rewards 
A few extra fights will ensure this bug will not effect me, but with all the other stuff this game has added to our plate, I am hard pressed to get all done. (GW, delves, dungeon and even daily tasks).
