I found this
[25-May-2018 20:34:42 UTC] ojs2: 404 Not Found
[25-May-2018 20:35:15 UTC] ojs2: 404 Not Found
[25-May-2018 20:35:41 UTC] ojs2: 404 Not Found
[25-May-2018 20:55:43 UTC] ojs2: 404 Not Found
[25-May-2018 21:02:30 UTC] PHP Warning: phpinfo(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone. in /home/k2542002/public_html/info.php on line 1
[25-May-2018 21:02:37 UTC] PHP Fatal error: Call to undefined function Symfony\Polyfill\Mbstring\iconv() in /home/k2542002/public_html/plugins/generic/citationStyleLanguage/lib/vendor/symfony/polyfill-mbstring/Mbstring.php on line 154
[25-May-2018 21:02:38 UTC] PHP Warning: mktime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone. in /home/k2542002/public_html/lib/pkp/lib/adodb/adodb-time.inc.php on line 1073
[25-May-2018 21:02:40 UTC] PHP Warning: mktime(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone. in /home/k2542002/public_html/lib/pkp/lib/adodb/adodb-time.inc.php on line 1073
I also found the issue in this thread OJS 3.1 blank index page - #2 by ojsbsb
@ajnyga suggested this and solve the issue
Have you tried to empty the template cache in cache/t_compile?
Does it mean all files in t_compile folder deleted?