Can someone help me?

[sly plover]

if you are sure the database is connected, make sure it's called before any mysql_format or mysql_tquery calls

show us the code where you connect and check it's invalid

example

    database_handle = mysql_connect(hostname, username, password, database, options);
    if(database_handle == MYSQL_INVALID_HANDLE || mysql_errno(database_handle) != 0) {
        print("->> FAILED TO CONNECT TO MySQL DATABASE <<-");
        SendRconCommand("exit");
    }

[fathom dagger]

but it feels strange because printf isn't showed in the logs

new connectionHandle;

#define SQL_HOSTNAME "127.0.0.1"
#define SQL_USERNAME "server_750"
#define SQL_PASSWORD "d5xgnykrlh"
#define SQL_DATABASE "server_750_som"