Heya!
This is an English speaking forum.
If the Simbrief import doesn't work, there unfortunately isn't anything we can do. This seems to be an issue on the WASM API, and we reported this to Asobo. They have confirmed the issue and will come back to us with more information to resolve this.
It could also be possible, that you turned off your Online functions in the options / they got turned off by the sim. The import will also fail if that is the case.