There may be multiple reasons for this, so do make sure to send us a ticket via this link if you need assistance.
One possible reason is that your Internet Service Provider is using carier grade NAT (CGN).
This means that your router is not supplied with a globally routable IP address but rather with an address that is shared among multiple customers.
This means that your router (and forwarded devices) are not reachable from the public internet.
We are looking into solutions to make Keezel2Keezel work on two connections that are behind NAT routing but it will take some time before that will work (if at all).
However, if you think that CGN is not the issue you're experiencing, please contact us.