Thanks for your kind comments.
Now a little more background ... Op is learning Linux server admin ... and it's a journey. Chosen OS for his test server is CentOS 7. OP probably missed this somewhere in the sea of docs, the firewall default for 7 is now firewalld, but servers comes with IPTables (4/6). On OP's server iptables was active. The new FW does have some nice features ... like a 'reject zone' which is pretty easy to deny an IP or range of IP's *any* access to the server.
But here was the real problem ... me thinks ... Op using 'Software Selections Repo' and had installed php-fmp as well as Apache that way. Even though I thought I had added the tweaks to php-fmp and apache, still couldn't get .css and .js files .... Moodle server wasn't reporting 503 errors even with debugging set to developer. Finally saw them using FireFox's Web Tools. Do know that 503 errors are hard to troubleshoot and everything I tried didn't work.
The 'Software Collections' repo is really for the purpose of running multiple things ... like PHP versions. It's sorta like Bitnami ... a one off thang ... uses /opt/rh/blah...blah ... for apache and php-fmp and for Apache. Documentation comes from one source ... nothing that contained Moodle tips/tricks/quirks. Apache for example has an '/opt/rh/httpd24/root/' ... which reminded me of running Bind DNS in a chroot jail. That sort of thing great for DNS ... only way to run Bind really ... but not so good for Apache and Moodle IMHO!
After fighting it for about 4 hours (this is a test server), decided that going back to stock with repo for PHP + using mod_php would be the eaiest path forward. To Op's credit, sent some brief instructions/thoughts about that and he took it from there.
Actually, there is another poster in these forums that has been having all sorts of issues and in re-reading some of those postings noticed a path ... /opt/rh/blah-blah. Hmmmm ... another confused SLC box? Hmmm .... is 1 and 1 = two?
Bottom lines ... if op chooses CentOS 7 (which is just as good as Ubuntu IMHO) one will have to use 3rd party repos ... period. The choice of repo's appears to make a difference.
For myself ... I like 'keep it simple stupid' ... paraphrased it might say 'keep it Stock stupid'!!! ;)
Not that anyone beginning Linux server admin is 'stupid' ... but one sure does feel like that sometimes.
Server admin is a journey ... as is Moodle ... never ending. Failure and changing directions might be in a noobie admin's experience in the beginning ... it's not really 'failure' ... it's more like learning what doesn't work best for them ... e.g. ways that don't work. What is it that 'they' say ... 'you don't know what you don't know'! .... until you do! ;)
'spirit of sharing', Ken