I'm using an iFrame to host an HTM form on a Wordpress page. The iframe displays the form on our site so that users can interact with it on the webpage. The .htm file is hosted on dropbox and the iframe code looks something like this:
<iframe src="https://dl.dropboxusercontent.com/spa/numbers/file/file.htm" width="1000" height="4100" frameborder="0"></iframe>
In the past, this has worked fine. The form has displayed perfectly on our site. Recently however, for some users the .htm file automatically downloads when the page is loaded, for others it displays correctly.
When viewing other stackoverflow posts, I've seen users say that the Content-Type of the .htm file needs to be 'text/html;charset=UTF-8' and after checking, that is what our files are set to.
I am completely lost. We haven't changed anything in months, so this is not the result of user error. It randomly started happening this week.