I just copy the source codes from https://developers.facebook.com/docs/reference/dialogs/requests/, JavaScript Example section, change to my API ID, then I can see the Dialog. but when I sent a Request to One or More Users, I always got the error:
An error occurred with xxxx. Please try again later.
API Error Code: 2 API Error Description: Service temporarily unavailable Error Message: User can't send this request: Unknown error
Did anyone encountered this before?
Facebook must have made some change over the past 12 hours. In your App Settings you'll have to add "App on Facebook" and this should allow your invites to work again.
I had an application that had the same problem and in my App Settings I only had "Website with Facebook Login" and "Page Tab" checked. When I added "App on Facebook" the invitations started to work again.
Note: Now, when a user sends an invite, the invitation will be directed to the app on Facebook as opposed to being directed to your website. For my application I had to add code to redirect from the Facebook App back to the tab.