Omeka S error with Universal Viewer

When I try to get Omeka S to show page I get this error in Universal Viewer:
Unable to load manifest

In Mirador I get:
SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data

I am running Firefox but it also does not work in Chrome.
In Chrome I get the same error as Firefox and in Chrome I get:
SyntaxError: Unexpected token ‘<’, "<!DOCTYPE "… is not valid JSON

I am running Universal Viewer version 3.6.7 and Mirador version
Omeka S is up to date.

I am guessing this is a network permissions error but I am not sure.

Are you able to post the manifest URL that Omeka is looking for?

It should be fixed in last versions of module IiifServer.