yes i tried all even sending manually to same server to capmonster its returning this
Object_reference_not_set_to_an_instance_of_an_object.
form code is below please check
<form method="post" action="
http://2captcha.com/in.php" enctype="multipart/form-data">
<input type="hidden" name="method" value="post">
Your key:
<input type="text" name="key" value="12345678">
<input type="hidden" name="CapMonsterModule" value="ZennoLab.AudioReCaptcha">
<input type="hidden" name="ParallelMode" value="true">
The CAPTCHA file:
<input type="file" name="file">
<input type="submit" value="download and get the ID">
</form>
if u want the audio mp3 i can upload it too somewhere