New server

Did you grant the new user all privileges for the database?

Changing the url from 5.6.3.4 to 5.6.4.0 will not work because you have not run the update routine as per my previous post (index.php/tools/required/upgrade?force=1).

Hello I have similar problem, itā€™s was crazy, i tried all versions of PHP. php versions 5.2 to 5.6 shows a blank page. PHP version 7.0 for my simcasts and 7.1 just shows ā€œPlease Install Zend Optimizer!ā€ and I canā€™t start with new srver. So if you have a complete download of files and database, my advice would be to give a copy of those to a developer to see if they can rescue it all for you, I did like I say. Yes may be it costs some money, but It works in future.