Hi sergiomagomes,
Thanks for your inquiry.
Considering that the structure and content of each document are different, the cause of your issue may be different. At present the latest free version is
Free Spire.XLS for .NET Version:10.10, we recommend you try with the latest version first.
If the issue still occurs, please provide us with your test code and your input file. Then we will investigate further.
Sincerely,
Rachel
E-iceblue support team