The selected ban is not valid, try again.

can't do the ban appeal for some reason cant chose anything from Existing bans

If you were banned by Sentinel anti-cheat you can not make ban appeal. It could also happen if you got an IP that is banned and your account itself is not banned.

and how to see this Sentinel anti-cheat reason for my ban ....

When you log on website it should show why your account is banned. Probably under "My account" section.

well nvm its dont say anywhere for what ... and yea its for no reason .. the reason its that im playng maybe :X