Hi
Some technical background:
the dynamicsnav:// protocal handler is just like the http:// and https:// ones. It means that if you (in windows) try to run "dynamicsnav://...", windows knows that it should open NAV with those parameters. Just like it would run your default browser if you try to run "http://..." or "https://..."
Windows needs to "learn" this from the registry where the protocol handlers are defined.
What happen is probably that this registry setup got corrupted/removed somehow - or you did not install the windows client (RTC client) properly (or maybe you are trying to use an old C/SIDE (development client) on a modern BC15??? BC15 neither supports C/SIDE nor windows client - only visual studio code and webclient).
To fix it i would suggest that you simply run the installer and deinstall your windows client and reinstall it (won't work if it is BC15 off cause :-) ).
If you are more technical minded, you can see this blog post where i play around with the protocol handler, even writing a script so it might work when you use a ClickOnce Windows client installation (in ClickOnce the dynamicsnav:// protocal handler is not supported):
https://www.dabbler.dk/index.php/2019/08/06/playing-around-with-the-dynamicsnav-protocol-handler/
Note: Only mess with the windows registry after taking a full backup. Messing with it is at your own risk, so don't complain if you break anything :-)
