Minecraft Realms won't work if username is changed

I recently bought Minecraft Realms just to have some fun with my friends, and more recently changed my username from OSXp3rt to Honeyblaze. Since the name change, when I click the Minecraft Realms button, it gives me the error seen in the screenshot below.

Steps to Reproduce:
1. Change username
2. Launch Minecraft
3. Click "Minecraft Realms".