Hello.
As an Arabic native speaker, I can ensure & certify to you that it's futile/worthless to have an Arabic alias, whilst playing Team Fortress 2, because the letters/characters in-game are disarranged and will seem peculiar to an Arabic native speaker.
i.e., your name: «الأمير السعودي», will be disarranged in-game, to being: «ا ل أ م ي ر ا ل س ع و د ي».
And perhaps this is the issue. The letters are being recognized as spam. And thus, preventing you from joining.