A little more info in case someone needs it since I can't edit my previous post.
Error in the browser console when trying to start a chat:
index.php?action=head:5 GET https://mlcnfriends.com/sachat/index.php?theme=default&cid=49&msg=test&_=1562446613152 500
Error from my server log when trying to start a chat:
Stack trace:
#0 /usr/local/www/nginx/Sources/Subs-Db-mysql.php(1171): SMF_DB_MySQLi->error('\n\t\t\tINSERT INTO...', Object(mysqli))
#1 /usr/local/www/nginx/Sources/Subs-Db-mysql.php(1487): SMF_DB_MySQLi->query('', '\n\t\t\tINSERT INTO...', Array, Object(mysqli))
#2 /usr/local/www/nginx/sachat/Sources/Chat.php(83): SMF_DB_MySQLi->insert('', 'mlcnf_2sichat', Array, Array, Array)
#3 /usr/local/www/nginx/sachat/index.php(115): savemsg()
#4 {main}
thrown in /usr/local/www/nginx/Sources/Subs-Db-mysql.php on line 1408
PHP message: PHP Fatal error: Uncaught Error: Call to undefined function allowedTo() in /usr/local/www/nginx/Sources/Subs-Db-mysql.php:1408
Stack trace:
#0 /usr/local/www/nginx/Sources/Subs-Db-mysql.php(1171): SMF_DB_MySQLi->error('\n\t\t\tINSERT INTO...', Object(mysqli))
#1 /usr/local/www/nginx/Sources/Subs-Db-mysql.php(1487): SMF_DB_MySQLi->query('', '\n\t\t\tINSERT INTO...', Array, Object(mysqli))
#2 /usr/local/www/nginx/sachat/Sources/Errors.php(65): SMF_DB_MySQLi->insert('', '\n\t\t\t\t\t mlcnf_2...', Array, Array, Array)
#3 /usr/local/www/nginx/sachat/Sources/Errors.php(51): logError('/usr/local/www/...', 1408, 'Uncaught Error:...', 'FATAL')
#4 [internal function]: shutdownHandler()
#5 {main}
thrown in /usr/local/www/nginx/Sources/Subs-Db-mysql.php on line 1408" while reading response header from upstream, client: 67.209.241.26, server: mlcnfriends.com, request: "GET /sachat/index.php?theme=default&cid=49&msg=test&_=1562446679926 HTTP/1.0", upstream: "fastcgi://unix:/var/run/php-fpm.sock:", host: "mlcnfriends.com", referrer: "https://mlcnfriends.com/index.php?action=profile;u=2;area=theme"
2019/07/06 16:58:43 [warn] 4267#101791: *62031 an upstream response is buffered to a temporary file /var/tmp/nginx/fastcgi_temp/5/11/0000000115 while reading upstream, client: 67.209.241.26, server: mlcnfriends.com, request: "GET /sachat/index.php?action=head HTTP/1.0", upstream: "fastcgi://unix:/var/run/php-fpm.sock:", host: "mlcnfriends.com", referrer: "https://mlcnfriends.com/index.php?action=admin"