Unable to Connect to CentovaCast Server

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I have a CentovaCast Reseller Account and I use the following redacted information to access my CentovaCast Dashboard:

Server URL/Port: http://cast1.<hostname>.com:<port> (my host uses cast1 instead of cast)
User Name: <username>
Password: <password>
Account Limit: 35

Pinging the domain name returns the IP address

I am using that information when adding the values to the CentovaCast API Module:

Server Label: CentovaCast

Hostname: cast1.<hostname>.com

IP Address: Ping result

Port: <port>

Username: <username>

Password: <password>

Account Limit: 35

I receive the following error message when attempting to add server:

An internal error occurred, or the server did not respond to the request.

A connection to the server could not be established. Please check to ensure that the Hostname, Username, Port and Password are correct.

Any advice on what I may be entering incorrectly? Do some hosts require a proxy or whitelist for API access?

Thanks in advance,

Doug