A Microsoft file hosting and synchronization service.
Dear Giulia Pantusa,
I'm sorry to hear that you're experiencing issues with OneDrive sync on your Mac. Appreciate you share with us the troubleshooting steps you have tried.
For the situation you encountered, we do understand the inconvenience caused and apologize for it.
I notice you mentioned "everything appears perfectly synchronized but some folders are missing that are visible online instead. In addition, one of the folders does not contain all the files, which instead are perfectly visible online. "
Does it mean that you can see all the files and folders from OneDrive Online, but some folders and files are missing in OneDrive sync folder on your Mac?
If yes, you may check if the missing files and folders are visible on the OneDrive Online. If they are, try to force a sync from OneDrive Online with steps below:
1.Unlink OneDrive and quit OneDrive App on your Mac.
2.Open a browser, access OneDrive Online, click Settings(the gear icon) from upper-right corner, click Sync this OneDrive, as shown below. (on the bottom of my reply)
Then go to check if you can see the folders and files in OneDrive sync folder on your Mac.
If the sync issue persists, I deeply understand how frustrating this situation can be and sincerely apologize for the inconvenience caused.
Considering that you have reinstall OneDrive and reset OneDrive, the best way to troubleshoot this issue further is to report it to the related team, as they have higher permission to remotely assist you and help you investigate the situation further, find the root cause and fix it. The support team has higher permission and more resource, this would be the most efficient way in handling this case for you.
Microsoft 365 Admin has right permission to contact the related team. Therefore, I sincerely recommend you contact your Microsoft 365 Admin, then follow steps in this support article Get support - Microsoft 365 admin | Microsoft Learn, raise a support ticket to contact the related team.
For reference: How do I find my Microsoft 365 admin? - Microsoft Support
Appreciate your patience and understanding and thank you for your time and cooperation!
Hope you have a nice day!
Sincerely,
Tina | Microsoft Community Moderator