Champion grade not appearing and not getting any champion xp after the game

I noticed this problem about 2 weeks ago. After ending a match of league (doesnt matter if I win or loose) no champion grading appears and i dont get any champion XP. At first it didnt bother me, but now it has happened too many times and it even cost me many S rank grading. As the picture provided shows I get a black screen with a loading icon where the champion grade appears. If i then go to the match histories the round doesnt show any champion grade. After looking a bit on the internet I found a 4 year old post that had the same problem so I was wondering if there is a way to fix it somehow, cos without getting any champion xp I cant level the mastery of my champions. If anybody knows how to fix it , would be really helpfull. (Heres the link to the old thread https://boards.na.leagueoflegends.com/en/c/bug-report/n6sbc5Mt-grade-not-appearing-after-games ) Edit: its not like the grade and xp dont load at start and maybe after some days I still get it, no. This past 2 weeks I tried to lvl up my miss fortune to mastery 3 and jinx to mastery 4 and although I played a lot (like maybe 5 rounds a day), only few would really count (like maybe 20% out of all).