Hey there @jontebarca
I'm sorry to hear you're having some problems launching your Assassin's Creed game due to a DX12 error.
Please note, that due to laptop limitations for Ubisoft games, we can only offer limited support.
To try and help you resolve this issue, I'd first recommend you make sure your GPU drivers as well as your operating system are up-to-date with the newest version installed.
I'd also suggest taking a look at the PC troubleshooting guide to see if any of the steps inside might help as well.
If the issue persists, please provide us with your laptop and GPU model, so we take a closer look.
Thanks!