EA app.
Since posting I tried to:
Disable firewall.
Uninstall the game, manually remove any registry entries, firewall rules, left over files (settings etc).
Reboot.
Redownloaded and installed again.
Flushed DNS caches, switched DNS servers.
Still didn't work ☹️
Finally I got a silly idea, I log out of the EA app and then log in again.. blam.. it worked!
What?
I could install/repair/uninstall from the EA app, even run some other old games I had installed, but not Apex.
Why only Apex was affected - who knows.
Some logging would be so helpful.. see where it gets stuck, logging failed network requests with IP/DNS names for instance.
Im a dev myself and there's no chance there isn't a detailed logging system in the game.. just give a CMD option to log to file and this would be so much easier...