You need to place forums onto debug mode. You have 2 ways to do so:
1) manual: requires edit of config.php (located under /includes/ directory), specific adding this line:
PHP Code:
$config['Misc']['debug'] = true;
2) automatic: download debug mode plugin:
https://vborg.vbsupport.ru/showthread.php?t=196422
This plugin will enable you with options to set debug mode on/off on both forums & admincp.