Cannot Connect To Portal

I set my dashboard to run on lion.bmi.emory.edu:3000. All is going well.

Now back to setting up the developer portal as above. This time, I did not use the same domain as you explained in this and the other (Panic Crash on Ubuntu X86 - #6 by Martin) thread.

I used the below as the new domain.
portal.tyk-local.com:8080

Please note that 8080 is configured as the portal port, as following the default configuration elaborated in the documentation.

Now, the dashboard throws the below error message, when I click “Set”.
“There was a problem updating your CNAME, please contact support”

tail -f /var/log/tyk-dashboard.stderr indicates the below.
time=“Jul 7 12:42:54” level=error msg=“INvalid domain supplied, not saving: portal.tyk-local.com:8080

My tyk_analytics.conf is as below.

"host_config": {
    "enable_host_names": true,
    "disable_org_slug_prefix": true,
    "hostname": "lion.bmi.emory.edu",
    "override_hostname": "localhost",
    "portal_domains": {},
    "portal_root_path": "/portal",
    "generate_secure_paths": false
},
"http_server_options": {
    "use_ssl": false,
    "certificates": [
        {
            "domain_name": "",
            "cert_file": "",
            "key_file": ""
        }
    ],
    "min_version": 0
},

So it is not the same issue reported in Setting up developer portals - #4 by Martin

What could have gone wrong? Pls note, I am running Tyk on Centos 7.