Losing all Comp points after a win


I have won a game on ranked with about 617 ranked points in g2 and the after playing a Brawl the next thing I knew was that I was put into demotion match. Can Blizz explain to me why the system got so messed up after I return to this game from an 8 month leave? This problem occured on the EU server btw. Naturally, I have taken 2 screenshots, one with my ranked points stat, the other with my match history stat 2 min apart.