When I tried the first example from FormFunction, Neat Examples it only worked once (for Wikipedia) and after that it always gave an error result (for example on Google or Wolfram Research). The example is:
CloudDeploy[
FormFunction[{"Website" -> <|"Interpreter" -> "SemanticURL",
"Input" -> "Wikipedia"|>}, Composition[HTTPRedirect, First],
AppearanceRules -> <|"Title" -> "WebGo!",
"Description" ->
"Write the name of any website, and we will take you there!",
"SubmitLabel" -> "Go!"|>]]
Even after closing the web page, and regenerating the CloudDeploy link, giving a new link, I could only obtain the error page. I could not even obtain the input form.
That was likely a temporary bug with HTTPRedirect. That code seems to be working now. However, I would suggest editing it to use the name of the input variable. I think much easier to read/understand:
CloudDeploy[
FormFunction[{"Website" -> <|"Interpreter" -> "SemanticURL", "Input" -> "Wikipedia"|>},
HTTPRedirect[#Website] &,
AppearanceRules -> <|"Title" -> "WebGo!",
"Description" -> "Write the name of any website, and we will take you there!",
"SubmitLabel" -> "Go!"|>]]