Hello! I see you're having trouble confirming battles against friends in the Warhammer 40,000 app on your Mac, where pressing "OK" to confirm the battle does nothing. Let’s get this sorted out together.

To start, could you tell me if you and your friends are all using the same version of the app? Also, have you tried confirming battles with anyone else or is it just specific friends? This info will help narrow down the cause.

Meanwhile, here are some steps to try in order:

1. Check for App Updates
Make sure your Warhammer 40,000 app is updated to the latest version. Sometimes bugs affecting multiplayer features get fixed in newer releases.

2. Restart the App and Device
Quit the app fully, then restart your Mac. Relaunch the app afterward and try again.

3. Verify Internet Connection
A stable internet connection is essential for online battles. Confirm your Mac is properly connected to the internet.

4. Review Time Zone and Region Settings
Sometimes battle invitations can fail due to mismatched time zone or region settings. On your Mac:
- Go to Apple menu > System Preferences > Date & Time
- Choose "Set time zone automatically using current location" if not already selected.

5. Check for Account or Friend Sync Issues
Confirm that your app is properly logged in to your Warhammer account, and that your friends list is syncing correctly.

6. Try Re-inviting or Re-accepting Battle Invitations
Have your friend send a new battle invitation and carefully watch for any on-screen errors during the process.

If these don’t work, there could be a deeper connectivity issue or a bug. Let me know what you observe after these steps, and I can help investigate further or suggest contacting higher-level support.

Are you okay with trying these first?