I don't know if this is appropriate to add to this page, but I thought that it might help someone.
On some websites my "username" is my email address. NOT on Wikipedia. I had habitually typed @gmail.com w/username in the "USER" field, and that won't work.
Now some of you are young and bright and will never make that error. At least not for a few more decades. But we have an aging population, and I'll bet I'm not the only one to make this mistake. Just sayin' ... ~~~~