Error no flight plan was found on this server

When I try to fetch a flightplan from the server i get the error message “Error no flight plan was found on this server”. The plan doesnt have to many words and it doenst work for every flight I try. I prefile the fligthplan via SimBrief maybe thats the problem? The probleme occured after I filed to flight plans after once 2 days ago but I cant find a way to delte any flightplan.