Problem with app Notes after update

The ONLY way to have encrypted the notes is by creating an encrypted notes password at the time you password locked them. You may not remember doing so, but it's the only way they could have been password locked. As others have suggested, you can guess as many times as you want, but until you remember the password you HAD to create to lock the notes, you will not have access to them. Apple can't help you here. The password is encrypted directly on your iPhone and there is no way to bypass it.

Passwords should always be written down somewhere when you create them for future recall. Once forgotten, it can be too late.

Unlocking Notes: Managing Passwords and Transitioning Touch ID/Face ID

Unfortunately, there is no option to reset the Notes password. However, you have the option to create a new password for the new notes you wish to lock or create.

The only course of action available is to continue trying different passwords, as there is no limit to the number of attempts.

You may know that Face ID / Touch IDs cannot be transferred from one device to another. Therefore, to ensure smooth access to your imported notes on your new iPhone, it is important to link the password to the new Touch ID/Face ID feature.

During the setup of your previous device, it is likely that you created a password and enabled Touch ID/Face ID for enhanced security. Consequently, any notes created on that device would exclusively rely on Touch ID/Face ID authentication. Consequently, it is highly possible that you have forgotten the password by now.

If you set a hint for locked notes, please utilize it to aid in recalling the password. If you didn't set a hint, you can attempt various passwords that you are familiar with.

Watch the 2 GIFs below about locked Notes.

You did set a password to encrypt those notes. FaceID is supplemental to the password as a convenience measure.

If you can’t remember the password you used to encrypt those notes, they are unreadable.

Olga_ejik wrote:

But I didn't enter a password, Face ID was set up immediately.

Yes. You did. You just don’t remember doing so.

The answer has already been given.