When users close the internet browser tab, the account remains open for more than 30 minutes and they cannot access again until that time expires. So this code will set it to 15 minutes instead of 30 minutes Add this code in wp-admin > Plugins > editor > select WPLMS Customizer Plugin > wplms-customizer.php
add_filter(‘wplms_login_threshold’,function($x){return 900;});
Here 900 is seconds which is equivalent to 15 minutes