Stupid question on changing URL of channel via Google+

[Doom Video Vault]

I recently changed my URL via Google+ and my name here even with the /Channel/ under the new name says it does not exist. What did I do wrong? Am I supposed to wait a day or two?

 

[LyfeWithDragons]

They made it to where you need at least 500 subscribers before you can get a personalized url

 

[Doom Video Vault]

I have over 700 and I chose /c/DoomVideoVault

 

[LyfeWithDragons]

Hmn, maybe it's already taken?

 

[Doom Video Vault]

As far as I know, Google+ would not have given me the option to change the name to it. I really just want to fix it, maybe @Michael could point what I did wrong?