In this thread you see that the user has done exactly what was expected, copy paste from documentations but still it does not work.
IFTTT integration issues - Configuration - Home Assistant Community (home-assistant.io)
This actually highlights an issue with documentation <–> Home Assistant.
If you copy the automation from the documentation then you get the “automation:” (script:, and possibly other) line also which should not be included.
But it’s still needed so that you can see where to post the configuration when you know what you are looking for.
As this probably mostly is an issue for new users perhaps the GUI could remove the header line if you paste that in the yaml box?