The issue was occurring for me on our corporate network and from my home machine. When debugging in the console, it looks like the URL resolved to https://us2-excel. Changing the URL to US1-excel.officeapps.live.com worked, and then tried just https://excel.officeapps.live.com

https://us1-excel.officeapps.live.com/op/embed.aspx?src=http://www.learningaboutelectronics.com/Articles/Example.xlsx

https://us2-excel.officeapps.live.com/op/embed.aspx?src=http://www.learningaboutelectronics.com/Articles/Example.xlsx

We changed the IFRAME URL to 'https://excel.officeapps.live.com/op/view.aspx?src=' and it works now.

Same issue is still occurring and also occurs on other websites that host the Excel web viewer. Most likely a Microsoft issue, but really odd for the service to be down so long.

When running the Playground "3. Population Excel" demo, the embedded Excel report displays 502 bad gateway error.

https://playground.jsreport.net/w/admin/V71OgRWt

502 - Web server received an invalid response while acting as a gateway or proxy server.

There is a problem with the page you are looking for, and it cannot be displayed. When the Web server (while acting as a gateway or proxy) contacted the upstream content server, it received an invalid response from the content server.

Has Microsoft changed how to embed Excel files?