Is this a new flight plan or one of the examples? When you say launch. Is this every time? But the error would suggest you are publishing to FS2020 at the time...? I would need the flight plan ps to recreate to reproduce here. If so can you press the menu button to the left of the flight plan and export flight plan. The e-mail to firstname.lastname@example.org Thinks
After some thought on this, I would suggest deleting the settings file, which is not removed by uninstalling.
HOW TO DELETE SETTINGS in windows file explorer type: %APPDATA% This will show the "Roaming" directory Then navigate back up one directory, and then to the "Local" directory and next "simEFBmanager-settings"directory