The "File Not Found" error is always cryptic. I would take a look at the Configuration sheet in the Governance Dashboard and see if there are two extra settings enabled. Check to see if "Append Custom Postscript" is enabled. if it is, try disabling it. Same with "Use Configuration Script". Try disabling those and see what you get.
I would start there and see what happens. If you disable those, or they are already disabled, we can look at other config options.
One last question. Has the Governance Dashboard ever refreshed successfully?