Error Message looks something like this:
Fatal error: Cannot redeclare enqueue_fullcalendar_locale() (previously declared in /home/xxxxxxxx/public_html/wp-content/plugins/erp/includes/functions.php:2218) in /home/xxxxxxxx/public_html/wp-content/plugins/wp-hr-manager/includes/functions.php on line 2313
Cause: WP-HR Manager and WP ERP both installed
Solution: Deactivate WP ERP (you may also need to deactivate WP-HR Manager and then reactivate it)