The username or password is incorrect, leading to a failure to connect to the database.
Host name error: an incorrect host name or IP address was specified, preventing connection to the database server.
Port number error: The specified port number when connecting to the database is incorrect, making it impossible to communicate with the database server.
Firewall blocking: The firewall settings blocked communication with the database server, resulting in a failed connection.
The database service is not running: The database service is not running or has been stopped, cannot connect to the database.
Configuration error: The parameters set in the database configuration file are incorrect, resulting in a failure to connect to the database.
Internet issue: difficulties in connecting to the internet, such as unstable or disrupted connections, leading to the inability to connect to the database.
Database permission issue: the user does not have sufficient privileges to connect to the database, resulting in a connection failure.
Database service failure: The database server is experiencing issues or is down, causing inability to connect to the database.
