Dear Francois Croteau
Welcome to Microsoft Community.
I understand that you are currently having a problem with the Send to OneNote feature. The email sends normally, but you can't find it in OneNote.
We were able to reproduce your issue during our recent testing, where emails sent to OneNote via this feature were delayed in appearing in OneNote, or did not appear in OneNote.
This issue may have something to do with the recent OneDrive data migration, which has caused many Microsoft users to have their cloud functionality disrupted. We currently recommend that you do not use this feature in the near future, and perhaps afterward, the feature can return to normal use.
Additionally, in order to make Microsoft developers aware of this issue, we also recommend that you report it to the developers through the feedback channel that comes with the OneNote application. Please open the OneNote desktop application and click "File" - "Feedback" to report this issue.
Finally, again, I apologize for the inconvenience this has caused you. But hopefully my response will make you aware of the recent anomalies in cloud synchronization for Microsoft accounts.
Best Regards,
LucyW-MSFT | Microsoft Community Support Specialist