Sometimes, when trying to use certain Office Timeline commands in Office 365, such as "Apply to All" or saving a custom template, PowerPoint for Office 365 freezes or hangs, or takes too long to apply your changes.
Go to File -> Account in PowerPoint.
Under "Product Information", click on Update Options -> Update Now.
Note: If the Update Options button is missing and you see an About button instead, it may be either because your company is using a Group Policy for Office updates or because you have a volume license install. In such cases, please contact your company's IT administrator.