Run netstat -alpn | grep <port> to check if Accumulate is or is not listening on the relevant port. A response like tcp6 0 0 :::16695 :::* LISTEN 20355/accumulated indicates that Accumulate is listening.
If Accumulate is listening, something is blocking or interfering with connections to the node. If you can connect to any port (including SSH or HTTPS), the issue is likely an incorrect firewall configuration.
Otherwise (if Accumulate is not listening),
Check if Tendermint is still catching up. Open http://<your-node>:<tendermint-rpc>/status in your browser, or make the equivalent RPC call.
If you get no response, use netstat to check if its listening. If it is listening, see above.
If it is not listening, wait for a minute to ensure the node has booted. If there's still no response, ask for help.
If you get a response and catching_up is true, wait for it to finish catching up.
If you get a response and catching_up is false, ask for help.
Prometheus is not responding to requests
When running a DNN and BVNN in dual-mode, the BVNN's Prometheus exporer is disabled. Because of how Tendermint initializes Prometheus (see here), the Prometheus exporter cannot be enabled for both nodes. If neither the DNN's nor the BVNN's exporter are responding to requests, see The node is not responding to API requests.
The base port for the testnet and mainnet is 16591. All of the node ports have a fixed offset from the base port.