Select the Unknown Password (Brute Force) mode if you don’t remember the password, and provide the details asked (optional):

After choosing Unknown Password (Brute Force) mode, tick the box which you remember are included in the password (optional):
Important Note: Please tick only those boxes where you are confident about the accuracy of the information. Do not fill in uncertain information.

Once the OneNote password recovery process is finished, a pop-up will comes up, and choose the OK button.

Finally, your complete password will display on the screen. Select the Copy Password option to copy your password.

Choose the Unknown Password (Brute Force) mode and provide known information like:
Important Note: Please check only those boxes where you are confident about the accuracy of the information. Do not fill in uncertain information.

Once the OneNote password recovery process is finished, a pop-up will come, and choose the OK button.

SysTools OneNote Password Recovery Tool