Seems like a server problem (not Machform). The bit that gives the clue is "unknown MYSQL server host......" so I suggest you check what the server name should be (ask your hosting support people this question). The server name (on standard Apache/Linux hosting) is usually simply "localhost".
Try putting "localhost" in the "server name" variable in the config.php file of your Machform setup, and see if that fixes the issue. Appnitro could also test this (if you submit a support ticket to them, through your Appnitro Member's area).
I'm not saying I'm correct, and only an assumption, based on what I think the error is saying. Otherwise, there might be a temporary issue with the MySQL server that will fix itself in due time.