Most issues are the result of mismatching configuration. However, failing to parse a SAML response is a more fundamental issue.
Are you certain it’s an HTTP Post of a SAML response that’s being received at the assertion consumer service endpoint?
How did you retrieve the SAML response XML to check its syntax?
If there’s still an issue, please enable SAML trace and send the generated log file as an email attachment to support@componentspace.com mentioning your forum post.
The log will show exactly what’s being received and why it can’t be processed successfully.