Have you accessed PWA Settings recently in Office 365 Project Online and seen a warning for “We have detected critical permission issues with your site. Go to Additional Server Settings page to learn more” like below:
Accessing the Additional Server Settings page shows you a new setting: “Reassign ownership & deploy fix” as seen below:
Clicking the “Learn more” option will load the Microsoft support document that details the steps to resolve – https://support.microsoft.com/en-us/help/4524338/mitigation-steps-for-dissociation-error-in-project-web-app As per the note under the “Reassign ownership & deploy fix” heading and the Important note on the support doc:
Ensure you resolve the issues as per Step 1 before clicking the Deploy Fix button in Step 2.
Modern Work Management - Project and the Power Platform blog 