after getting S- or S i still havent been able to get a chest from few days

Have you already gotten a chest on the champion you're playing?You can only get one chest per champion per season, so if you are playing a champion that you have already gotten a chest on, then you cannot earn another chest on that champion.

for somea reason i don't have this problem atways 3+ chests but try to go with ppl that don't have chest becouse your entire party gets chests if one of you gets it