Troubbleshoot IIS customer site

I have a custom app that was created 2 years ago, the devs are no longer available. it uses IIS to host a small webserver that allows data to be captured by patients/cleints via webpage

The webform submits perfectly fine on the server but when I try to goto the webpage on another computer or on a tablet the form will not submit.

I need an expert in iis.. and javascript , webpages to figure out the issue.

Attached is the iis web files and the enviroment installation for iis.