Having Issues With Changing Username

I want to change my username because I created it years ago when I was still young and I'd rather have all of my accounts on creative platforms under the same username, just because. However, whenever I go to the "Account" tab under my settings and try to change it, the "save" button remains faded out. It doesn't what I do, it won't let me change my username. I have tried typing in my current password in the uppermost textbox, I've tried filling out all the textboxes with the proper information, and I've even tested if the username I want is unavailable by keyboard smashing into the textbox, but the "save" button always stays faded. I'm considering trying to create a new account and merging the two, but I am hesitant to try that option unless I know for sure that it will work... Is there anything else I can do?