Problème avec la mise à jour 21h1

Hello Kylian_15, 

Please run Windows Update troubleshooter from Settings app > Update & security > Troubleshoot > Additional troubleshooters. See if it works.

If that doesn't work, try this:

Open administrative Command Prompt and type following commands one-by-one followed by Enter key.

net stop wuauserv

net stop cryptSvc

net stop bits

net stop msiserver

Ren C:\Windows\SoftwareDistribution SoftwareDistribution.old

Ren C:\Windows\System32\catroot2 Catroot2.old

net start wuauserv

net start cryptSvc

net start bits

net start msiserver

Close Command Prompt and see if Windows Updates works then.

If you still unable to install 21H1, I recommend you to upgrade to Version 21H1 via ISO file.

Refer this step-by-step guide:

https://www.kapilarya.com/how-to-upgrade-to-windows-10-using-iso-file

Let us know if this helps!

Note: Included link in this reply refers to blog post by a trusted Microsoft MVP.