Key not set after update
You have not yet set your store's secret key in the configuration file!
Use the "tebex:secret <secret>" command to update it without having to reload the plugin.

I set my key in config and do this ingame to but i get always this message

Hey there! Those messages are from our old plugin - please ensure that you've removed the old TebexDonate plugin, and replace it with the updated Tebex 2.0.2 plugin here: https://umod.org/plugins/tebex#updates