I would request a support to solve this problem that seems to be something simple but still have not found the solution.
According to research on the internet form should be getting initialized, but have not found a way to do it in the Action allowing the form to be loaded on the request.
Not sure if this is the real problem.
I'm putting all the files involving the situation, appreciate the cooperation in advance.
File 01 - DocumentoEscaneadoAction.java
File 02 - EnvioDocumentosEscaneadosForm
File 03 - action-mappings.xml
File 04 - form-beans.xml
File 05 - struts-config.xml
File 06 - envioDocumentosEscaneados.jsp
File 07 - Stack-trace