Yeah the api over the UDF is not working with mine either. I'm sending captchas via their command line tool.
Also I've made two functions to send / report them but I think they're outdated now - you can still give it a shot if you want to.
Code:
Func _DeathByCaptchaCmdDecode($sUsername, $sPassword, $sCaptchaFile)
If FileExists("response.txt") Then FileDelete("response.txt")
RunWait(@ComSpec & " /c ""deathbycaptcha.exe -l " & $sUsername & " -p " & $sPassword & " -c """ & $sCaptchaFile & """ >> response.txt""", @ScriptDir, @SW_HIDE)
Return StringRegExp(FileRead("response.txt"), "(\d+) (.+?)" & @CRLF, 3)
EndFunc
Func _DeathByCaptchaCmdReport($sUsername, $sPassword, $iCaptchaID)
RunWait(@ComSpec & " /c ""deathbycaptcha.exe -l " & $sUsername & " -p " & $sPassword & " -n " & $iCaptchaID & """", @ScriptDir, @SW_HIDE)
EndFunc