Trying to access MBL via internet but getting error message HTTP Status 404

I have been able to get the MBL to connect on my local network but trying to access via internet gives me error message
"HTTP Status 404-TCP relay failed.

I have seen a couple of posts about cable modems and routers. Not to savy in this area.

Network layout is cablemodem-wireless router-MBL

Thanks in advance

The Dashboard UI is internally configured not to be accessible from anywhere outside of the local area network.