HAZZAH! Hairpin NAT has solved my problem. Now that I configured a Hairpin NAT in my router, I can 1) Use my dynamic DNS server from my local network, 2) No longer need to switch my server back and forth from local host to my DDNS.
I wish I had known to do this sooner. It would have saved me so much trouble.
https://en.wikipedia.org/wiki/Network_address_translation#NAT_loopbackBug #2: WC-RCP iOS Connects to ddns.net from local (on WiFi) network (This is the same network the WC-RCP server is on.), acknowledges the server from the Manage WeatherCat Servers page, but reports that it is not a WC-RCP server on Channels, Reports, and etc pages. This is not a high priority bug in my opinion, it's just a little misleading.
This is not a high priority bug in my opinion, it's just causes a little confusion at first.
The next time a "...is not a WeatherCat server" appears, tap the appropriate radio button for the server you are using. This will cause a retry which usually fixes the problem.
If you send me your URL in a message and I will attempt to reproduce the bug.