Well this error says mailwizz cannot connect to the database, maybe your mailwizz credentials for db have changed?
The database info is stored in apps/common/config/main-custom.php in case you need to adjust it.
Reinstalling mailwizz won't help you.
Things are simple, the error is there because for some reason mailwizz can't connect to your database server, there's absolutely nothing mailwizz can do to help you go over this. Have your hosting look into the issue and see why it can't connect, i have my money on the mysq/server limitations.
I am guessing the same about the mysql connectivity thing but our hosts support is a concern.. let me check...otherwise I would keep the current installation and make a new folder on the same domain and install a fresh piece..and then transfer the old db to the new one.. will that work?
The MySQL queries for the above mentioned databases are getting killed by the server which is causing the intermittent issue with the site loading. You can verify the same from cPanel >> Health checks and Monitoring >> Mysql Killed Queries.
Please note that, the long_query_time set for the MySQL service is 15 seconds.
Since it is a shared server, we can't alter this values for single domain. We have set this limit carefully to avoid any wastage/abuse of server resources and increasing the limit will result in degradation of server's performance.
Hence, we strongly recommend to contact your developer and optimize the database queries and PHP scripts for the better performance of the site.
At least my hunch was right.
They can strongly recommend what they want, if they give you limited resources, i can't do magic here.
If your number of subscribers is very high and the shared hosting can cope with it, then go with a VPS.
In the DB config file where you have mentioned to connect to localhost - I changed it to the server IP and it worked ... it was not connecting to the mentioned localhost mysql socket but the IP worked..
Also, would request if you can remove the uploaded screenshot as it has the db and username details mentioned..for security purposes..