The officeatwork Apps and Add-ins use an encoded and encrypted refresh and/or access token to keep users signed in. These tokens are stored in the browser's cache allowing the add-in to silently sign-in as long as the tokes are accessible and valid.Browser cache not persisted.Silent sign-in will not work if your browser or entire device can not persist with any browser cache.Refresh token expiredSilent sign-in will not work if the tokens available are expired. This can happen when a user does not sign in for a long period and/or the refresh token's life cycle has been set to a short period in your tenant's Azure AD settings.