Please research online how to set correct file permissions for nginx on CentOS - if the above command does not solve the problem then unfortunately I do not know what the solution is.
777 permissions are not typically recommended as they open the files up to any users and groups on the CentOS system.
For installations within /usr/share/nginx/html on CentOS, the following should work, although this can change depending on your particular setup!
chown -R nginx:nginx /usr/share/nginx/html
The chown command will change the ownership of the files to nginx so it is able to write to the files as required.
The error in the logs is as follows:
PDOException: SQLSTATE: Syntax error or access violation: 1071 Specified key was too long; max key length is 767 bytes
Unfortunately this means that your MySQL/MariaDB database version is too old - we recommend MySQL version 8+ or MariaDB 10.2+, although it should work with MySQL 5.7.22
If you are using a web host, please contact them regarding the database version.
Which operating system on the VPS are you using, and in which folder is Nameless installed?