When you enter your info on Your TruckersMP settings site you're not supposed to enter your nickname but your community URL, if you have a custom URL in your steam profile settings you can also use that.
You have entered Superspeed2000 which is your profile name but multiple people can have the same name. However only one person have your community ID which is 76561198208505459 .
Just enter that and you'll be good.
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