Hi @Enrico Carretti
You may navigate to Services (services.msc) and confirm the WebClient service is in running state.
Then open Credential Manager > go to Windows Credentials > Generic Credentials > remove credentials which is related Microsoft 365 and OneDrive.
If the issue still persists, I suggest you removed the OneDrive Mapping, and re-doing it.
Besides, turn off two-step verification with your OneDrive Microsoft account temporarily, check if it has anything to do with account security. https://support.microsoft.com/en-gb/account-billing/how-to-use-two-step-verification-with-your-microsoft-account-c7910146-672f-01e9-50a0-93b4585e7eb4
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