The iframe you have tried to embed is currently not from an authorised domain.
https://clients6.google.com/static/proxy.html?usegapi=1&jsh=m%3B%2F_%2Fscs%2Fapps-static%2F_%2Fjs%2Fk%3Doz.gapi.en_US.yeXBLUPFVB0.O%2Fam%3DwQ%2Frt%3Dj%2Fd%3D1%2Frs%3DAGLTcCMlnwewRAov0AZPyVUNbTC2eJu5ZA%2Fm%3D__features__#parent=https%3A%2F%2Fcalendar.google.com&rpctoken=759834581
To discuss the options around adding your content please contact the support team at swssupport@detcorpcomms.zendesk.com.