Nice and Great Article!
For blank response with no error : try only text data first, date field may be more difficult.
For error check this:
Important:
The list GUID must be formatted as: {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}. If the list GUID has the hyphens and braces escaped (with %7B for the opening brace, %2D for the hyphens, and ...