Twitch username problem?

Ni
- in Twitch
5

Hey I'm trying to change my username. I haven't done that since 2017 (if someone thinks it only works every 60 days anyway).
Everything runs paletti until I try to enter my new username: I have checked it 20 times, but Twitch says that the username is not available.
There's no one with my username, I'm sure. And I find it stupid to put a character or a number behind it.
Does anyone know the problem and a possible solution?
(I don't want to add my username or my new one here for troll protection).

Bu

Another user name.

Ni

The name I want to rename myself to has been used for everything for over 5 years. I'm far too attached to him that I would simply change him.

Di

The account with the name was named.

Ni

? What?

Di

Oh, I'm sorry, I mean banned.