1. Connection configuration error: It may be that the Redis connection parameters configured in the Idea are wrong, such as IP address, port number, password, etc. Need to carefully check whether the configuration is correct.

2. Network communication problem: It may be that there is a problem with network connection, which makes the Idea unable to connect to the remote Redis server normally. You can try using other tools or command-line tools to test whether the connection is normal.

3. Server access restrictions: If the remote Redis server is protected by a private network or firewall, you may need to provide corresponding access rights before connecting. You need to ensure that the machine where Idea is located has legal access rights.

4.Redis service failure: The remote Redis server may fail, such as the service is not started and the memory is insufficient. You can check the logs of the remote server or use the command-line tool of Redis.

In terms of expansion, we can further introduce the functions and characteristics of Redis, such as high-performance in-memory database, support for multiple data structures, distributed cache, and common usage scenarios, such as session management, data cache, leaderboards, etc. In addition, technology stack related to Redis can be mentioned, such as Redis cluster, master-slave replication, persistence and so on. In order to understand and solve similar problems more comprehensively.