(Realms) Error Message: mco.errorMessage.404

Today I bought a subscription for Minecraft Realms, and when I opened the Realms menu to start it, it gave me the error message "mco.errorMessage.404".
If I exit, and go back into the Realms list, it's empty but the error doesn't pop up- and I'm not sure how to fix it or to start my new Realm.

• I had a texture pack at first, but I disabled it, and still the same.
• Created a new profile (Copy of X) and it did nothing either.
• My internet connection seems fine.

I'm not sure how to fix this, but I do just really want to play. I can't seem to find the answer anywhere. I can give whatever info you need, I just want to be able to play! Thank you!

EDIT:

• Friends were able to log into my account and access Realms perfectly fine from their computers.
• Clicked Edit Profile, set to keep launcher open. Asked friends to do the same, then try to open Realms. Mine says Realms version "1.6.1" while theirs says "1.7.56" both.