PDF couldNotBeFlattened

Hi! All

Our team has been leveraging OneSpan createPackage API to create package and call the signingURL to successfully eSign PDF forms leveraging text anchors. 

All these forms which were uploaded prior to calling CreatePackage were expected to be Flattened and has been working well in executing eSignatures.

Hi Team, I am trying create a package with pdf document part of package. I am getting below Error. {"messageKey":"error.validation.verifyDocument.couldNotBeFlattened","message":"Could not upload PDF document: it contains a syntax error preventing proper processing of its data.","code":400,"name":"Validation Error"} The PDF File i am using has PDF FORM Sigature Fields which were prepared by XML/SOAP based silanis Integration module. I have created Approval block with field to Extract existing Signature Blocks in PDF Form.