Can you try to connect using netcat? If the port is open and the connection works correctly, you should see /multistream/1.0.0 as the first message
This example shows connecting the public gateways (you can do CTRL+C after seeing the multistream message)
$ nc gateway-int.ipfs.io 4001
/multistream/1.0.0
Replace gateway-int.ipfs.io 4001 with your IP and your port (defaults to 4001, only use 4003 if you made a choice to change it by changing the config)