I confirmed that the antenna is connected correctly, tried connecting it to other ports, but then it will not see a network. I confirmed that networks are available in the diagnostics, but when I put the SIM in and try to connect, it always fails.
Thanks for reaching out.
There could be a few reasons why this is happening. Please see this link where you can find some common solutions that should help.
Feel free to post a few photos of your Ringo so I can check if your soldering looks okay.
Stay in touch!
-Marija from CircuitMess
Make sure the SIM card is inserted as shown in the picture. The gold contacts need to be toward the front of the phone and the notched corner needs to be visible (even when the card is fully inserted) and toward the top of the phone. There are 4 ways the card will fit but only one way it will work