Kevin,
Do you have OSPi running on your Pi when you check it on canyouseeme.org? The OSPi code is what responds to port 80 or port 8080. Make sure you can browse to the Pi from “inside” your network before configuring the router and checking it through canyouseeme.org. It does not matter if the device is attached to copper ethernet or using WiFi for connectivity as far as the router and port forwarding are concerned. If the Pi answers on port 8080 (for example: http://192.168.0.33:8080) then make sure the port forwarding configuration on your router forwards port xxxx (for example 88) to 192.168.0.33, port 8080. Then to access OSPi from outside your network (public Internet) you should browse to (http://publicIP:88) where publicIP is what is reported on canyouseeme.org as “Your IP:”. The outside (public) port does NOT have to match the port that your OSPi actually responds on. You just have to map an accessible, not firewalled port to your inside device via the router’s “port forwarding” service…
When I use the canyouseeme.org page and I supply the forwarded (external) port, it finds my OSPi just fine, by the way.
Hope this helps and doesn’t muddy the waters too much!