500 error thrown while adding a government pdf

Silanis.ESL.SDK.EslServerException: Could not upload documents to package. Exception: The remote server returned an error: (500) Internal Server Error. HTTP POST on URI https://sandbox.e-signlive.com/api/packages/e-c31K6_hT0TsAYj0n9EepjxjyY=/documents. Optional details: {"messageKey":"error.internal.default","technical":"error.eslx.inputValidation.documentPreVerifyInvalidResponseNumberError [#20db89f5-e8c8-4587-b53b-12364457fe76]","message":"Unexpected error. We apologize for any inconvenience this may have caused you, please try again. If the problem persists, please contact our support team.","code":500,"name":"Unhandled Server Error"} ---> Silanis.ESL.SDK.EslServerException: The remote server returned an error: (500) Internal Server Error. HTTP POST on URI https://sandbox.e-signlive.com/api/packages/e-c31K6_hT0TsAYj0n9EepjxjyY=/documents. Optional details: {"messageKey":"error.internal.default","technical":"error.eslx.inputValidation.documentPreVerifyInvalidResponseNumberError [#20db89f5-e8c8-4587-b53b-12364457fe76]","message":"Unexpected error. We apologize for any inconvenience this may have caused you, please try again. If the problem persists, please contact our support team.","code":500,"name":"Unhandled Server Error"} ---> System.Net.WebException: The remote server returned an error: (500) Internal Server Error.
   at System.Net.HttpWebRequest.GetResponse()
   at Silanis.ESL.SDK.Internal.HttpMethods.MultipartPostHttp(String apiToken, String path, Byte[] content, String boundary, AuthHeaderGenerator authHeaderGen, IDictionary`2 headers)
   --- End of inner exception stack trace ---
   at Silanis.ESL.SDK.Internal.HttpMethods.MultipartPostHttp(String apiToken, String path, Byte[] content, String boundary, AuthHeaderGenerator authHeaderGen, IDictionary`2 headers)
   at Silanis.ESL.SDK.RestClient.PostMultipartPackage(String path, Byte[] content, String boundary, String json)
   at Silanis.ESL.SDK.Services.PackageService.UploadDocuments(PackageId packageId, IList`1 documents)
   --- End of inner exception stack trace ---
   at Silanis.ESL.SDK.Services.PackageService.UploadDocuments(PackageId packageId, IList`1 documents)
   at Silanis.ESL.SDK.EslClient.CreatePackage(DocumentPackage package)