Hi Ian,
I have already added the app to the windows firewall as being allowed to go through, and I have reinstalled it.
As I also follow the other topic (I didn’t see that before I made this one), I think this issue is on your side, as Richard states.
https://forum.navigraph.com/t/fms-data-manager-is-not-finding-any-addons-cant-add-addons/3206/9