1. Verify that YugabyteDB is running
First, ensure that the expected YugabyteDB processes are running on the current node. At a minimum, the tserver process needs to be running to be able to connect to this node with a YCQL client or application.
Additionally, depending on the setup, you might expect a master process to also be running on this node. Follow the instructions on the check processes page.
2. Check cluster-level issues
Next, check the list of cluster issues and the respective fixes for each of them.
3. Check logs
Inspect the YugabyteDB logs for more details on your issue. For more details on where to find and how to understand the YugabyteDB log files, see Inspect logs.
4. File an issue
If you could not find a solution to your problem in these docs, please file a GitHub issue describing your specific problem.