Facebook Instant game bot message sending works locally, but fails after uploading to App Engine...

Facebook Instant game bot message often results in "Cannot send Instant Game message to user at...

Leaderboard.getEntriesAsync - request failed for >=20 entries...

failed to submit Leaderboard score in facebook instant games...

Launching Facebook Instant Game from web...

Instant Games Content Security Policy...

Facebook Instant "PLAY" button not present...

(FB Instant games) How I can get payload data from Game Play Button?...