I think after disabling SeLinux it started to work for him. Not sure if there is an issue with the SeLinux part or not in the installation notes.
I enabled SElinux
Re-enable SElinux:
sudo setenforce 1
Temporarily change the context for DATA + subfolders:
sudo chcon -R -t httpd_sys_rw_content_t /opt/webwork/webwork2/DATA
Test to see if the error is still resolved, and if so, make it permanent:
sudo semanage fcontext -a -t httpd_sys_rw_content_t "/opt/webwork/webwork2/DATA(/.*)?"