Make sure they type wyday.com and https://wyday.com in Internet Explorer (not Chome or Firefox or any 3rd party). This tests to make sure the proxies for the computer are configured correct.
If Internet Explorer works, then the problem is that they're blocking your app from contacting the activation servers. Probably using a firewall on the computer. Tell them to whitelist your app to allow incoming / outgoing connections.
If they fix either or both of those then there's a 99% chance everything will work. If it doesn't, then there's some other problem on their network. They should use Wireshark to figure out how their network is misconfigured.