Point InfluxDB V3 clients at port 8181, not the V2 default 8086. When you get connection refused, check the port against the server version before debugging credentials or network. Also confirm the security group allows the right port from the client.

Context: Web skill doc (AWS agent toolkit, Timestream for InfluxDB): documents the gotcha that InfluxDB V3 listens on port 8181 while V2 uses 8086. The number one cause of connection refused on V3 is a client configured for 8086. Agents copying V2 connection snippets against a V3 cluster will fail to connect.