I have the same eror. client is on android. in one network.
Guys, we need more information here…
According to here:
This may be related to not using https for connecting with the App on mobile.
my rocket chat server is on http not on https and accessed on static ip simply via port forwarding, just when using android app it return the above mentioned error
You need HTTPS in order to use it from mobile.
this means that i cant use it on android till DOOMS DAYS as per ur answer 
hehehe.
Don’t quote me on that, but It may work if the device IP is on the same network as the server IP.