Cannot Open Master Chest But I have keys....? Please Help

I can't for whatever reason use my keys to open my master chests. It all started when I received a gem and turn it into a master chest and key. I then went to use the chest and for whatever reason when I tried to open it it said I needed a key so I then went and purchased $5 dollars worth of riot points just to try and buy a key and chest and it still won't let me open the chest but I can open normal chests though. Please Help me. Thanks