Hey there @munkoria, thanks for taking the time to get in touch, I am sorry to hear that your problems are persisting.
We're not aware of any active issues regarding this error message. Therefore can you please once more fully reinstall the game and supporting software, and then run it as administrator for me?
If you continue to experience problems, could you please reach out and create a case through the Ubisoft Support website? Also, when doing this, could you please attach your system files? These files will greatly assist our investigation. Once the case has been created, one of our specialists will be able to take a closer look into why this might be happening.
For anyone else who comes across this thread, and has been experiencing this "unrecognised game client" message after going through the troubleshooting previously provided by my colleague and myself, could you please also reach out and create a case through the Ubisoft Support website?
If you are experiencing issues creating a case, please note that we have other social media platforms available where you can also reach out to a specialist. You can find our dedicated Facebook and Twitter support here.