Error establishing a database connection

have checked, double-checked, triple checked, changed passwords, changed database users, confirmed and reconfirmed the wp-config.php, checked host name – all is exactly as it’s supposed to be as described by the host and by wp installation guide. what’s missing? should I be running the install.php from the host’s admin panel or something? can’t find a browser web browser as part of the host’s admin panel. i’m simply putting the address into the broswer on my pc

thanks in advance
mark