And btw , you could probably test with the Button on the Device as well. Don’t over think it or make it more than it needs to be.
Do you have good green LED’s on both units?
Send a message from one to the other first , then Back.
Then look at the radio config , section. They did all the Low level coding for you. Think higher level triggers and messages.
each can cause the other… if that makes sense.
Assign the Button GPIO on one Stack to blink the USER LED assigned on the other S3 (a little hard to see) but you can test it from end to end with what you have there.
HTH
GL 
PJ 
all you need is a USB power bank and your on the way! 
" To use a GPIO pin on a Meshtastic device to send a message, you can leverage the Canned Message Module or the Detection Sensor Module. The Canned Message Module allows pre-defined messages to be sent when a button (connected to a GPIO) is pressed. The Detection Sensor Module allows you to monitor a GPIO for high/low status and send text alerts when a change is detected." from G-man
I’m picking up some nodez.,…
man the web looks better…
