That sounds strange, peharps you have some issue with your WordPress setup.
Please review https://codex.wordpress.org/Debugging_in_WordPress
especially check your config file
// Enable Debug logging to the /wp-content/debug.log file
define( 'WP_DEBUG_LOG', true );
/wp-content/debug.log will only have something if there is something to debug
when you are certain you have debug set up, disable and enable the plugin, this will definitely write to debug.log assuming your wordpress is set up correctly. If you still don’t get a wordpress debug log then you have another issue e.g. permissions
in which case you probably be best served on the wordpress forums for trouble shooting