#2 Oct 11, 2016 00:40
To my knowledge, there is no change that would explain that between 6.7.4 and 6.7.7.
The 404 page is from you web-host, not from b2evolution. It means that the problem is before b2evolution gets a chance to execute. This looks like an htaccess file issue.
Verify that you did not accidentally damage/modify your
.htaccess file during upgrade.