As much as I struggle to make MailWizz compatible out-of-the-box with any host, this is just unrealistic since the configuration vary so much between the hosts.
By default, MailWizz runs in production mode, that is, no errors are show to the end user. That also means that if you get a serious error (most of the time a file permission error) the application will stop running and you will get a white screen.
If this happens, most probably you will open a support ticket but in order for me to be able to help you, you will have to enable debugging so that i can see exactly the error.
In order to enable debugging, all you have to do, is to open the ‘apps/init.php’ file and at line 16 add:
Then save the file and reload the app in your browser to see the actual issue.