A family of Microsoft products that enable users to capture, organize, and reuse notes electronically.
Take a look at this 1 year old problem. It most likely does not apply, but I suppose it may ...
2016 01 02- Unable to customize Outlook Today, QAT or the ribbon since the last Windows 10 update
Yes, the QAT file may be locked by mistake. The first thing to try is just restart the computer. This will close out any locked file indicators.
If that doesn't work, this article tells you where to find the file that contains QAT customizations. Try renaming the file. This will wipe out all of your current customizations, then you can try starting over.
Backing up all Ribbon and Quick Access Toolbar (QAT) customizations at once
https://www.msoutlook.info/question/backup-ribbon-and-qat-customizations
After making several changes to the Ribbons and Quick Access Toolbars in Outlook, I wanted to make a backup of my customizations.
There is an export button for this in the “Customize Ribbon” and “Quick Access Toolbar” section of the Options dialog but this only backs up the customizations for the current item window and not all the item windows which are available in Outlook. This makes the exporting process quite cumbersome.