i have a problem with the level 6 shards

hi i am phantomslark and i have a problem with the level 6 shards.last time when i played a match i got a s- with xin zhao and for that i got a level 6 shard for xin zhao and i already had one so i had what i needed to make xin zhao level 6 and he even had level 5.When I wanted to make him level 6 it told me to have him permenetly and i had him when i pressed the thing, i couldnt unlock level 6. I dont know if it is a bug but please help me. -_-