Hi Anton:
I checked the apache error log file and there is a consistent error that is generated whenever an attempt is made to use that menu item. The error message is shown below. Hope this helps. Thanks.
[Mon Aug 01 12:29:30.583272 2016] [:error] [pid 3165] [client ::1:34674] PHP Fatal error: Uncaught Error: Call to undefined function simplexml_load_string() in /var/www/html/playsms/lib/fn_core.php:823\nStack trace:\n#0 /var/www/html/playsms/plugin/core/gateway/fn.php(197): core_xml_to_array('<?xml version="...')\n#1 /var/www/html/playsms/plugin/core/gateway/gateway.php(210): gatewaydisplay()\n#2 /var/www/html/playsms/inc/app/main.php(33): include_once('/var/www/html/p...')\n#3 /var/www/html/playsms/index.php(34): include('/var/www/html/p...')\n#4 {main}\n thrown in /var/www/html/playsms/lib/fn_core.php on line 823, referer: http://localhost/playsms/index.php?app=main&inc=core_welcome
[Mon Aug 01 12:33:25.748427 2016] [:error] [pid 3167] [client ::1:34678] PHP Fatal error: Uncaught Error: Call to undefined function simplexml_load_string() in /var/www/html/playsms/lib/fn_core.php:823\nStack trace:\n#0 /var/www/html/playsms/plugin/core/gateway/fn.php(197): core_xml_to_array('<?xml version="...')\n#1 /var/www/html/playsms/plugin/core/gateway/gateway.php(210): gatewaydisplay()\n#2 /var/www/html/playsms/inc/app/main.php(33): include_once('/var/www/html/p...')\n#3 /var/www/html/playsms/index.php(34): include('/var/www/html/p...')\n#4 {main}\n thrown in /var/www/html/playsms/lib/fn_core.php on line 823, referer: http://localhost/playsms/index.php?app=main&inc=feature_sms_autoreply&op=sms_autoreply_list
[Mon Aug 01 13:06:00.454679 2016] [:error] [pid 3165] [client ::1:34982] PHP Fatal error: Uncaught Error: Call to undefined function simplexml_load_string() in /var/www/html/playsms/lib/fn_core.php:823\nStack trace:\n#0 /var/www/html/playsms/plugin/core/gateway/fn.php(197): core_xml_to_array('<?xml version="...')\n#1 /var/www/html/playsms/plugin/core/gateway/gateway.php(210): gatewaydisplay()\n#2 /var/www/html/playsms/inc/app/main.php(33): include_once('/var/www/html/p...')\n#3 /var/www/html/playsms/index.php(34): include('/var/www/html/p...')\n#4 {main}\n thrown in /var/www/html/playsms/lib/fn_core.php on line 823, referer: http://localhost/playsms/index.php?app=main&inc=core_user&route=user_config&op=user_config