Quite late, but: does anyone remember how they fixed this, and if that might have been related to a non-unique AppEUI?
And @markruys, was the following indeed the AppEUI that was actually used? If yes, then it’s not the correct length and maybe TTN will have added a leading zero. But as it doesn’t look like a registered, unique EUI to me, I assume the real AppEUI was simply redacted in the post:
The following seems to suggest that a non-unique AppEUI might be one of the causes of the error message:
(I’m not having this problem myself; just trying to understand things for future readers.)