It sounds like your OpenSprinkler has a wifi router acting as a client to your main network. It also sounds like you have a double NAT situation instead of bridging the second device.
If this is the case, you can proceed in one of two ways:
1) Switch the “client router” into bridge mode, this will allow your main router to see OpenSprinkler.
2) Forward the port to your “client router” and then also forward the port for OpenSprinkler on the client router. That means you have to perform the port forward twice (once on the main router and once on the client router).
Hope that helps!
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