Well, the exception “java.lang.IllegalArgumentException: Invalid row index” has many scenarios. Since you are using an older version (Aspose.Cells for Java v17.12) so we cannot evaluate your issue. For your information, we enhanced Aspose.Cells APIs lately and we recommend you to kindly try using our latest version/fix: Aspose.Cells for Java v20.3.x. If you still find the issue with v20.3.x, kindly provide sample Java program (runnable) and template files (if any) to reproduce the issue, we will check it soon.
I was able to find the root cause of this issue and fix it and it from our app code - we were going over the 1million plus mark for excel and it was throwing that exception. Thank you for the details.