SimpleBrowser - Click a button on a Web page

Good morning,

I'm trying to upload a file online and send this file loaded after clicking the button. All this using the SimpleBrowser. However, in no way can I click this button, I believe that something from the site itself is preventing the click. I do not know how to solve it. I need some hint. It follows a part of the code.

1) Save the file in the required location 2) Click to Send (but do not load)

       browser.Find("input", FindBy.Name, "field(-manter-arquivo)").Value = sArquivo;
       browser.Find("form", FindBy.Id, "enviarpliForm").SubmitForm();