It sounds like the websockets are not working which could likely be caused if you are using a proxy that's not configured for it. Can you share how you have the URL being directed to Mango. We use Apache with a virtual site to act as a proxy and had issues getting the websockets to work.
Here are some general instructions we put together that might be helpful:
Login to VPN server and enable Websocket proxy module in Apache (just has to be done once, don’t need to do it every time):
a2enmod proxy_wstunnel
Go to Apache websites configuration directory:
cd /etc/apache2/sites-available
Backup the website config file you want to set for Websocket proxy:
cp -pr <yourwebsite>.conf{,.bak}
Where <yourwebsite> - is the name of config file, usually the same with website name.
Edit the file <yourwebsite>.conf in your favourite editor and add below text:
RewriteEngine On
RewriteCond %{HTTP:Upgrade} =websocket
RewriteRule /(.) ws://<Mango_IP>/$1 [P,L]
RewriteCond %{HTTP:Upgrade} !=websocket
RewriteRule /(.) http://<Mango_IP>/$1 [P,L]
Where <Mango_IP> - is the IP address of a Mango device to which you configured ProxyPass.
Reload Apache configuration:
service apache2 reload
