In most cases WoW2GO will tell. If you see something like this:
then it definitely not working. Depending on reason for failure, WoW2GO may start to complain as soon as you press Start button or wait until you actually try to login into WoW.
NOTE: It is advisable, to try to Start newly created configuration (as opposite to Play). You may see that something wrong right away. Also, it is good idea, to run WoW in window mode (so you can see WoW2GO) when you trying to connect via newly created configuration.
NOTE: Full list of error messages could be found here.
There are endless number of reason why WoW2GO may not work (and not all of them WoW2GO's fault). Below you will find 2 most common ones.
Reason number one is that there is no Proxy/Server running at the host you configured or it is running on port other then you have configured. Simplest way to test if this is actually the case is to configure Proxy settings accordingly in System Preferences/Network/Proxies (assuming it is not already configured this way) and see if you still can browse the web.
NOTE: Use Safari for this test. Safari will follow proxies configuration to the letter (and will fail if there is no proxy), other browsers may try to connect directly to web server in case proxy does not work.
NOTE: In this situation WoW2GO may report one of following messages:
Quite often network administrators will restrict kind of connections which are permitted to go through the proxy. It is especially true in case of HTTP proxies. In most cases, HTTP proxy will be configured only to allow HTTPS traffic (port 443).
NOTE: In this situation WoW2GO may report one of following messages:
The only way around is to find different proxy/server.