we set up a system to book Hot Desks using Microsoft Bookings. We then wanted to embed the Booking System onto our Sharepoint news site for staff.
I built the page and using the iFrame code from the Booking page, I pasted it into web page using Embed.
At first, it told me I did not have permission to add an embed from this site, so I went to Site Permissions and added outlook.office365.com using this option: "Allow contributors to insert iframes only from the following domains."
Following that, I was able to successfully add it to the page. Everything was looking good on my end (I could see the iFrame) so I published the page and sent it companywide. However, everyone that clicks on it sees this (see attachment)