This is your problem. It sounds like the systems are working great, RTCM is flowing between units.
A base needs to Survey-in outdoors. A rover needs to be outdoors. All antennas must be L1/L2 or better. You need a clear view of the sky to achieve <20mm accuracy. Otherwise, you’ll get positional fixes but not RTK Fix.
I wanted to post a quick update here. I did end up going the phone route based on suggestions. Hotspot on my phone on the tripod where the base station is so it can talk to RTK2GO. Borrowed another phone to connect to the rover and incorporate the correction data in SW Maps.
I did get the first few use cases completed, but it was not a streamlined process. The firmware on the Postcard is very glitchy. I had to learn the exact order and timing to change settings and reboot to get things working. SW Maps would also crash after every 20 to 40 points I located.
I was very pleased with the accuracy. But I would not recommend this setup to anyone until the software is ironed out. I’ll check for updates before I need to use it again and report back if it fixes the issues I was having.