Hello Michael

Thank you for your purchase.

Can you please send me the connection credentials in a PRIVATE message, so I can test it from my end?

These errors usually imply that the server you're connecting to has some additional security. Try whitelisting your site's IP address and see if that helps.

Also, ask the hosting provider on which the separate DB connection is if there are some additional settings that are required for the login.

Hello again Michael

Can you please check if you have the following drivers installed, and activated?

These drivers need to be installed and activated on the server where your WordPress website is. After you install and activate those drivers, it should work fine.

The server has its own method of establishing the connection, and we're using PHPs logic of connecting to separate connections. The errors that you see are what your server returns, so there's no additional log within wpDataTables that would distinctively show you what's behind the error.

The most commonly used is SQLSRV. Other than being installed and activated, make sure to check with your hosting provider if there are any additional security measures that are required to log in to the separate DB (this assumption is based on the 1st error message "connection refused").

Hi again Michael

We don't have any similar screens, but you can see all drivers in wpDataTables/System Info:

Those are all PHP drivers from our server. Unfortunately, each server has a different configuration, so I can't advise you to turn any of these off. If you turn off nd_pdo_mysql I can't say what's going to happen, since there are probably other services that use this driver, and it could break some segments of your website.

Can you reach out to your hosting provider and ask them if it's safe to turn off/on drivers there?

Hi again Michael

Looking at this section it appears as if you have all the necessary drivers installed:

PDO extension: - PDO Drivers: mysql, dblib, odbc, pgsql, sqlite, sqlsrv

There are no system requirements that you need to have since the plugin works in a WordPress environment. All you need are the drivers listed in one of my previous responses. Have you checked with the hosting provider if they are all enabled (not just installed, but also enabled)? Since you were able to connect to this database from our sandbox, I wouldn't say there are any special requirements for the server on which the database resides, but instead something on the server where WordPress is installed.

For MSSQL connections you need either sqlsrv or odbc, which you have installed (just check if they're actually active), so using nd_pdo_mysql over pdo_mysql would make no difference (you're connecting to MSSQL, nor MySQL, so those are not even being used in your case).

Are you maybe using Plesk? One of our customers reported a similar issue which turned out to be an issue with the server being behind a draconian firewall and IT wasn't very found to opening ports to the exterior. The issue was about the different routes Plesk uses for PHP as it stores them at /opt/plesk/php while the default folder is /etc/php that also existed so the drivers were being added to the wrong place.

Can you have your hosting provider check that as well?

Hi again Michael.

I checked with our developers and they said the issue is coming from the website's server. It could be a number of things, from setting the drivers (which I believe you have set up correctly), to a firewall blocking the connection.

There are a lot of things that can cause this, and there are also a lot of solutions. Please have your hosting provider check these points:

https://stackoverflow.com/questions/8511369/adaptive-server-is-unavailable-or-does-not-exist-error-connecting-to-sql-serve

https://stackoverflow.com/questions/37205752/sqlstate01002-adaptive-server-connection-failed-severity-9/46679322

You will need to check if the database contains an SSL parameter, as mentioned here: 

https://stackoverflow.com/questions/37317242/how-to-know-if-connection-to-database-is-using-ssl-or-not

You can also check out the following thread for MySQL and PDO:

https://stackoverflow.com/questions/9738712/connect-to-remote-mysql-server-with-ssl-from-php

I really hope this can help.

Hi again Michael.

I honestly don't know about shared hosting - there are a lot of limitations with it, so it could be possible.

There are a lot of hosting providers that work nicely and SiteGround is actually one of them. Personally, I'd go for GoDaddy or HostGator, but you can take a look at this list for best hosting providers for WordPress.

Also, make sure to get dedicated, not shared hosting.