I have also have purchased the new Flarm fusion and had some problems. Connection with SD was possible using the GDL90 compatable device option, but with that SD shows no bearingless targets (modeS), only flarm and ads-b. For bearingless targets SD needs the Flarm protocol, but selecting Flarm (with airconnect) in third party devices did not connect.
I have been in contact with SD and Flarm concerning this, and have now received information via Flarm that SD and Flarm worked together to solve the problem.
SD has released a beta version to test, were you can directly select the fusion in third party devices.
I tried it, and immediatly connection was made, and SD also shows the bearingless targets! Worth a try!