After so much praise can't let go.
Seriously, there are technical reasons too. We have a strong clue of the cause: It is the system upgrade. (I'm assuming that your provider hasn't moved your site to a new machine, nor completely wiped out the old system and installed the new system. Nobody does that. Rather it was a "dist upgrade" through scripts provided by CentOS.) Moodle won't restart in new system could only mean that some critical components are missing. Then the solution is simple; Install the missing parts.
The focused method is to find out (through debugging and phpinfo) what exactly is missing. If that is too tedious, you can try a fuzzy method by starting to install PHP modules. The compulsory ones for rel. 3.9 are iconv, mbstring, curl, openssl, ctype, zip, zlib, gd, simplexml, spl, pcre, dom, xml, xmlreader, intl, json, hash, fileinfo, xsl and mysqli. That'll take off Moodle just enough to report further problems through its GUI.
There could be second reason: That your hosting provider is involved in the process. The "big" generic hosting providers don't know Moodle. What they care is WordPress, which is hundred times simpler. And the worst part, they are used to tighten ("harden") the server for WordPress. If such an unknown (to us) precautionary measure is blocking Moodle, it is not going to leave. You'll be back at square one.
And you will be doing the helpers a favour by digging the cause. Letting go leaving it for speculation is not a good feeling. So, if you haven't already wiped out Moodle, follow the detailed instructions in Ken's previous post.
Seriously, there are technical reasons too. We have a strong clue of the cause: It is the system upgrade. (I'm assuming that your provider hasn't moved your site to a new machine, nor completely wiped out the old system and installed the new system. Nobody does that. Rather it was a "dist upgrade" through scripts provided by CentOS.) Moodle won't restart in new system could only mean that some critical components are missing. Then the solution is simple; Install the missing parts.
The focused method is to find out (through debugging and phpinfo) what exactly is missing. If that is too tedious, you can try a fuzzy method by starting to install PHP modules. The compulsory ones for rel. 3.9 are iconv, mbstring, curl, openssl, ctype, zip, zlib, gd, simplexml, spl, pcre, dom, xml, xmlreader, intl, json, hash, fileinfo, xsl and mysqli. That'll take off Moodle just enough to report further problems through its GUI.
There could be second reason: That your hosting provider is involved in the process. The "big" generic hosting providers don't know Moodle. What they care is WordPress, which is hundred times simpler. And the worst part, they are used to tighten ("harden") the server for WordPress. If such an unknown (to us) precautionary measure is blocking Moodle, it is not going to leave. You'll be back at square one.
And you will be doing the helpers a favour by digging the cause. Letting go leaving it for speculation is not a good feeling. So, if you haven't already wiped out Moodle, follow the detailed instructions in Ken's previous post.