We have three possible workarounds that may solve it:
Disable IPv6
- Close CK3
- Go to Control Panel > View Network status and tasks > Change adapter settings (left side)
- Find your Hamachi Connection and Disable it
- Find your Internet connection adapter (for me, it was WiFi)
- Right click your internet adapter and select properties
- Scroll down to find "Internet Protocol Version 6 (TCP/IPv6) and uncheck the box
- Select Ok
- Start up CK3 and should work.
Disable all other network adapters
- Go to Windows Control panel.
- Click on Network & Internet.
- Click on View Network Status.
Quick Tip: You can also quickly access these settings by right-clicking the network icon in the taskbar and selecting the Network & Internet settings option.
- Click on Change adapter options.
- Right-click all network adapters that are not connected to the internet and select the Disable option.
Use a VPN
- Obtain a VPN
- Set the country to the US (why this works is also an enigma ><)
- Start the game
- Sign in and see if it "sticks"