Hey everyone!
Firstly, just wanna let you know that I did merge multiple threads into this one big one to keep everything in one place.
Thanks your all your reports and sharing of workarounds.
This has been forwarded to the relevant team for investigation. In the meantime, please check if Rainbow Six and Uplay are whitelisted in your antivirus software.
Please note that we would advise against disabling your antivirus, even if this could be the cause of the issue. You could temporarily disable this for testing, but please make sure you re-enable it afterwards.
If you still have issues which does not seem to relate to your antivirus, please check this
article. If you still have issues after doing the steps in the article, at the bottom it explains how to create a ticket with system files so we can assist further.
Thanks!