Custom URL Won't Connect Despite Port Fowarding Success

I first apologize as I'm sure that this forum likely gets this question often but I'm clueless at this point. I've set up Subsonic and can get on the server with IP:4040 (where IP is the IP address of the server) and the automatic port fowarding option in settings says 
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Succesfully fowarding port 4040
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(URL) is registered but could not connect to it (ConnectTimeoutException)
