IronSecureDoc Troubleshooting Page Index Null Exception ERROR-401 ByChaknith Bin November 2, 2021 Updated June 22, 2025 Share: Description: This error indicates that the optional optional_specify_page parameter in the POST request has been set to a negative value. Resolution: To resolve this issue, make sure the optional_specify_page parameter is set to a positive integer if you want to specify a single page. If you intend to cover all pages, set this parameter to null or 0. Chaknith Bin Chat with engineering team now Software Engineer Chaknith works on IronXL and IronBarcode. He has deep expertise in C# and .NET, helping improve the software and support customers. His insights from user interactions contribute to better products, documentation, and overall experience. Ready to Get Started? Start Free Trial View Licenses >