Can't open locked notes on my MacBook Pro (2019)

It would appears there is some Feature in the note of Notes Application on iOS 16 that Monterey macOS 12.6 does not yet understand and / or is not able to use ( Function ).

Then would suggest two possible solutions ;

1 - Get Support Choose a product and we’ll find you the best solution.Start now and open an Apple Support Ticket as they are Apple Employees to deal will these types of issues . 

2 - Product Feedback - Apple and make it known to Apple regarding this ongoing issue 

mishta20 wrote:

hi, just an update

the solutions was determined to be to reinstall macOS Monterey. i unfortunately do not have the space on my mac to do this and don't want to fiddle with my files to make space at the risk of data loss (i am an honours student, i cannot risk losing files).

all the staff were very helpful - i have decided to wait till the next software update is released and install that. if issues persist i will have to cull some files to clear some space, and contact support again.

Q- " the solutions was determined to be to reinstall macOS Monterey. "

A - Not sure what Method the Apple Support Person suggested but there are two very different methods.

One involves Erasing theComputer and " Reinstalling macOS "

Then, there is the " In Place " Reinstallation. This method does not touch personal files, setting and installed applications. It basically Reinstalls the Operating System Over the Existing installation. It would over-write any missing or corrupted System Files

Q - " (i am an honours student, i cannot risk losing files). "

A - In either case. it is always a good Idea to Protect your Personal Files at All times.

A - Do you have a Rescue Plan In-Place. This comprises having 3 Backups using 2 methods and 1 Off Site incase of Theft, Loss or Natural Disasters. A Time Machine Backup  is very useful.

A - For addition purposes - two Tested Clones each to separate external drives. This is insurance incase the upgrades goes sideways. At least one Tested Clone and / or Time Machine Backup should be Off - Site

Q - " i continued receiving help over the phone where i was directed to put my mac into recovery mode (i think it was called), and reinstall macOS from there - the employee suspected i may have a corrupt version of macOS. however i needed over 10GB more space to do so. the employee then suggested my mac wasn't able to completely install the previous update as i did not have enough space - which i found to be a bit odd since it doesn't normally let you install updates when you don't have enough storage, and i wasn't stopped from updating to the latest software.

i am already tight with my storage and so there wasn't much i could delete so i decided to end the services there. "

A - Then to be forwards about this, the computer appears to have More Than the One Original Issue at hand If left attended to, the computer will struggle to perform well and consistently and may at some point Cease to Function at all

A - It is suggested to keep at least 15%  to 20% of the Drive Total Capacity as Empty Space for good operations of the computer and for additional updates to Monterey to download, expand and install.

Example; Total Drive Capacity of 500GB @ 15% equals 75GB Empty Space and 20% equals 100 GB Empty Space . Not having 10 GB of Empty Space is reaching the threshold of the compeer Ceasing to to Boot Up at ALL.

Should that happen - all the Important Personal Data is at Risk and the User ( you ) maybe required to -->> Transfer files between two Mac computers using target disk mode to try and salvage your Data

Followup.

Using an iPhone 14 with iOS 16.0.2 with Monterey 12.6 and any Notes I create on iPhone do work on Monterey 12.6.

The Caveat is, None of my Notes are Locked.

Perhaps that is the real issue and worth mentioning to Apple Support

Welcome and do keep us posted on the outcome - time permitting

Welcome but the " Rescue Plan " outlined earlier, for this situation, is going to do exactly that " Rescue " this should the eventual Cease to Boot Up occurs.

But, that is a Users ( your ) choice