Hey there meirmouyal,
If you used your device's passcode or login password to lock these notes, you won't be able to view them on iCloud.com.
To check if this is how your notes are set up, use the steps here:
1. In the Notes app
on your Mac, choose Notes > Settings, then click Set Password. If you have multiple accounts, first click the “Locked notes” pop-up menu and choose the account you want to set a password for.
Note: You can also create a password when you lock a note for the first time.
2. Do one of the following:
* Use the login password for your Mac for locked notes: Click Use Login Password. (If your notes are in an iCloud account, you must have two-factor authentication enabled and turn on iCloud Keychain in System Settings to use your login password for locked notes. If you have additional devices, they must be using iOS 16 or later or macOS 13 or later to see notes that are locked using your login password.)
* Create a custom password for locked notes: Click Create Password, then enter a password in the Password field. Enter the password again in the Verify field, enter a hint, then click Set Password.
For additional help with removing or changing the way the Notes are locked: Lock your notes on Mac - Apple Support
Guidance on how to view notes: View notes and locked notes on iCloud.com - Apple Support
Take care!