You can change it once every 90 days.
I cant seem to change my username...

On April 4th, it said I could change my name in April 8th because I changed it previously before. I tried to change it now, but the change button is not appearing. Does anyone know why?
There's no button at all by your username under Settings > Profile

Yeah I already did, they are changing it for me now Thank you!
The support is ok. Maybe will take sometime. Major bugs will not be fixed. Like my rating problem.
On April 4th, it said I could change my name in April 8th because I changed it previously before. I tried to change it now, but the change button is not appearing. Does anyone know why?