Help on embedded (full) html not being executed in Drupal 8

I have embedded html code (with input format “full html”) but the code is only being displayed, not executed.

I’m re-implementing functionality from a running D6 site to a new D8 site. The running site has embedded html (Facebook feed) in a block, and I want to do the same thing in D8, but haven’t made the html to execute. I copy the working html code from D6 into a D8 block, set input format to “full html” but the html code is merely displayed — not executed — in my block. Pasting the same code into a “basic page” also merely displays — but does not execute — the html.

Input format is set to “full html”, with no limit on allowed html tags. Content is being created with “administrator” role. (I’ve also switched themes, with no effect)

I verified that my html code, if opened as a file by my browser, produces the desired content..

Suggestions?
Thanks!
John

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/22/feed