I don’t know about other browsers, but the click zones are “off”, in Chrome.
To add an attachment, don’t click on "Add File.
Just mouse over the word “Subscribe” on the line below and you will see the tooltip … “No file chosen”. Click here to add your attachment.
As I mentioned in another post, if you do not see a “Subscribe” box, just move your mouse DIAGONALLY away from the SOUTHWEST corner of the “Add File” box. When the “No file chosen” tooltip appears, THAT’S where you click to add your file!
It is my understanding that the software used for this forum is a commercial package, provided by a third party. (I have seen it used by other forums). In that case, it may not be possible for SA to fix, in-house.
The software is Kunena https://www.kunena.org/
Its free and open source.
The problem is related to the template and an offset of buttons. I don’t know how to fix this!