New Username registers in mojang.com and minecraft.net but no in game.

I just change my Minecraft username about 8 hours ago. The name shows on mojang.com and minecraft.net. But it's not showing in single player chat and whenever I try to join a server, it says (Failed to connect to server - not authenticated with minecraft.net).
I have tried joining two different servers. I have restarted Minecraft and my computer multiple times.

Notes

• I have changed my Minecraft username before