These days, every web page contain a scripting programming language called "Javascript" that run on visitor's web browser. If it is disabled, the functionality of the website becomes unavailable or limited. So, if you are facing the same issue with Invoice office, than turn ON the JavaScript.
Learn How to Turn ON the JavaScriptSecondly, If you are not able to preview the document or invoice you created than enable the pop-ups in your browser.
Learn How to enable pop-ups in your browser
