I have a website developed with HTML and CSS.
This website has buttons for making selections and move from one page to the next one. All buttons' code is like this:

<form action="target_URL" method="post">
<h2 class="h2button">
<input type="submit" value="Enter" class="lists_button">

During the last few weeks, some persons have told me that nothing happens when they press the button, it is, the page stays where it is and does not go to the next one.

Any idea of what could be the problem here?

Thanks a lot!!!