Hi @Demarco,
I found this doc User Guide for Cisco Digital Media Player Device Manager 5.4.x - DMP Access and Security Settings, which may help you regain access.
https://content.cisco.com/chapter.sjs?uri=/searchable/chapter/www.cisco.com/content/en/us/td/docs/video/digital_media_systems/dmp/user/guide/5_x/5_4_x/dmpdmug54/access.html.xml
If that doesn't work, you may need to resort to remote commands. This discussion explains how to do that:
URL to send remote control commands to a DMP
https://community.cisco.com/t5/other-collaboration-subjects/url-to-send-remote-control-commands-to-a-dmp/td-p/1568389
Finally, if you do finally get access to edit the HTTP, remember to use the !DOCTYPE element, as well as meta fields. They might look something like this:
<meta content="text/html;charset=utf-8" http-equiv="Content-Type">
<meta content="utf-8" http-equiv="encoding">
I hope this help!