@Guillaume Lannes-Lacrouts
Hi,
What method or tool do you use to upgrade the version?
When the rollback appear, what's the detailed error message?
From the official website:
https://learn.microsoft.com/en-gb/windows/release-health/status-windows-10-21h1
We are initially throttling up availability over the coming weeks to ensure a reliable download experience. As a result, the update may not be offered to you right away. For more details, see How to get the Windows 10 May 2021 Update.
The fastest way to get the upgrade is through Media creation tool or ISO file.
Please download Media Creation Tool from the link below and select Upgrade this PC at the first screen:
https://www.microsoft.com/en-us/software-download/windows10
Hope above information can help you.
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