World of troubles installing ERPNext on CentOS 7 with mariaDB and Nginx server

Yes that’s the question - your startup seems reasonable.

You have checked SELinux to eliminate that as a possible problem source?

You will find other install notes for CentOS for comparison *SOLVED* Install.py now FAILS on Unbuntu 14.04, Debian 8, Centos 7. What happened? (also same on Ubuntu 16.04) *SOLVED*

Debian is the most common for installs.

EDIT: Note this for general what to try ideas Blank Login Screen After Upgrade To V8