Password Error changing Username

I tried changing my username twice, the name was taken, so I tried with similars (not leaving a space, underscores, etc.), but since the third try, when I type my password it just says that this one is missing or incorrect. I'm sure it's not incorrect, I tried this a lot of times, even copied what I wrote in a note pad to check if I worte it correctly, but it keeps happening.

I tried resetting my password, and it seemed like it worked (it led me change the password correctly), but when I tried again the issue was still there. I even tried deleting my account and starting it over again, but nothing happens.

I could really use some help with this, since I want to use my artistic username for my account. Thank you