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, itās 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 āPlease Install Zend Optimizer!ā and I canāt 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.