In core/local.config.php make sure that this part of code is like this below
# Debug mode is off by default
Config::Set('DEBUG_MODE', true);
Config::Set('DEBUG_LEVEL', 2); // 1 logs query errors, 2 logs all queries
Config::Set('ERROR_LEVEL', E_ALL ^ E_NOTICE);
this will put all errors in core/logs/log.txt
Let us know what is in this file and we might be able to help or else you could contact somebody to enter your ftp and have a look at it