Hello,
Please try the following.
Close all open files and quit any running apps. Be sure to close any files stored in your Personal Vault.
Click the "Unlock Personal Vault" button in the error message.
If a screen requesting identity verification appears, such as "Verifying user," follow the on-screen instructions.
The contents of your Personal Vault will be displayed, so confirm its status (there should be no Xs or other icons).
Right-click the "OneDrive" icon in the bottom right of your desktop, click "Lock Personal Vault" from the menu that appears, and check for any errors.