This issue can be caused by your Office365 administrator changing their security settings to disallow all add-ins that have not been approved by your administrators.

If they either disable this restriction in the Office 365 admin system or add your add-in's manifest to the allowed list, after some propagation delay (minutes to days depending on the number of individuals in your Office365 tenant) you should find your add-in opens as normal.


It sounds like you're hitting a timeout error. Make sure you're always handling calling Office.initialize() before any other code.

For example, I would call registerServiceWorker() from within your init method. You have a lot of things going on in there and it is firing off at the same time as initialize at the moment.

Office.initialize = () => {

  ReactDOM.render(<App />, document.getElementById('root'));


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