Ssh in.
Run this to open the editor:
nano landingPage/templates/landingPage.html
Then find the line that says this:
<a href="#" onclick="javascript:window.location.port=5080">
And change the 5080.
You can also take the pi out, and edit that file on the sd card. It will be home/pi/landingPage/templates/landingPage.html
What browser and OS are you accessing from to get that error?