Thank you. I tried checking the troubleshooting. None works.
To add, these are the errors I found on my log files.
[Mon Nov 27 10:44:19.216973 2017] [ssl:warn] [pid 8720] AH01909: localhost:445:0 server certificate does NOT include an ID which matches the server name
[Mon Nov 27 10:44:21.337870 2017] [ssl:warn] [pid 8754] AH01909: localhost:445:0 server certificate does NOT include an ID which matches the server name
[Mon Nov 27 10:44:22.066678 2017] [core:notice] [pid 8754] AH00094: Command line: '/opt/redmine-3.4.3-1/apache2/bin/httpd.bin -f /opt/redmine-3.4.3-1/apache2/conf/httpd.conf'
[ 2017-11-27 10:44:24.0952 8763/7f5161c2e700 age/Cor/SecurityUpdateChecker.h:452 ]: Security update check failed: Problem with the SSL CA cert (path? access rights?) while connecting to https://securitycheck.phusionpassenger.com:443/v1/check.json ; this might happen if the nss backend is installed for libcurl instead of GnuTLS or OpenSSL. If the problem persists, you can also try upgrading or reinstalling Passenger (next check in 24 hours)