Whenever I opened OneNote 2016 or 2019, the error To sync this notebook, sign in to OneNote popped up. Normally I just click on the notification. Then I see the Sync icon next to the name of the notebook, and then everything works fine. Not very disturbing, but because it is mainly annoying I figured it out and described the solution below.
Solution for error To sync this notebook, sign in to OneNote
To be on the safe side, before following the step by step guide, make sure you know the username and password of how you are logged into OneNote. This can be a Microsoft account, or for example an account of your company. You need the user details to log in again later

How to fix error To sync this notebook, sign in to OneNote
Step 1: Open Credential Manager

Click Start, type credential, and click Credential Manager
Step 2: Backup credentials (optional)

As an optional step, you may want to back up the current cached credentials.
Click Windows Credentials
Then click Back up Credentials and follow the steps to save the credentials to a *.crd file, Again, this step is not required but may become handy.
Step 3: Locate the MicrosoftOffice16 credentials

In Credential Manager, click Windows Credentials
From there, scroll down to MicrosoftOffice16:ADAL:xxxxx
Step 4: Remove all MicrosoftOffice16_Data entries

Expand each MicrosoftOffice16_Data entry by clicking the downwards arrow.
Then click Remove to delete the cached user credential. Do this until all MicrosoftOffice16_Data entries are removed.
Step 5: Open OneNote 2016

Open OneNote. The error To sync this notebook, sign in to OneNote should not appear. You may have to sign in once again into your account, because you removed all cached credentials. However, in most cases, OneNote will just single sign on (SSO)
Thank you for this!!! It was very helpful!
Thank you for leaving this kind comment, Jennifer!
This worked perfectly for me, thank you very much for the clear write up!
Does not work for me. There are no MicrosoftOffice16 credentials on my computer.
No Microsoft16:ADAL:
THANK YOU
Also on my computer, there are no MicrosoftOffice16:ADAL:xxxxx
records there. Instead of the ADAL part, there are several records with SSPI, live, orgid, OAUTH2. Some for Office 15, others for 16.
Have no idea what these are and therefore it is not clear to me if I should delete those or if that would other damage. Do you know if I should?
This worked for me. Thank you.
I’ve tried to do all of this. The first solution seemed to work, as there were no Windows Credentials. Don’t know how this is possible. I recently messed up my notebook in an extreme way & since I ‘fixed’ it, it’s not worked right since. I don’t know if I even added the IP address correctly as nothing in the cmd thingie looked quite like what the instructions said. And deleteing the Office 2016 stuff, again, restarting it seemed OK, then nope. I thought I’d log out & back in again, no one suggested that, but I just installed MS… Read more »
Deleted all Office data credentials. No improvement. Restore function worked. Problem still present.
Thanks! It worked for me. Great article.
This did NOT work for me. My company service desk had me try this, but the error remains even after a reboot. When I click to sign in, I get an error dialog that says “The server you are trying to access is using an authentication protocol not supported by this version of office“.
My company recently moved from the GCC Commercial cloud to the GCC High (Gov) cloud and that is when it broke.
Resolved! My help desk then said to do the following because our migration had changed locations of my saved files:
To fix this issue you need to change where your OneNote is saving to.
To do this, open OneNote and go to file > settings > properties > change location then chose the company OneDrive GCC High and you should be good to go. (you have to do this for every notebook you have defined in OneNote. Not sure proper fix if someone shared a notebook out to you, the might need to share it again)