HC12: Sketch stopped working suddenly

Hi guys,

my Setup:

HC12 modules (4)
Micro,
Nano,
Uno
IDE on a Macbook

I downloaded a sketch to configure the HC12 modules, which worked flawlessly. I played with the settings and finally reseted them to factory settings.
After the reset I again successfully connected them.

Now I tried the same some days later and they won't connect at all.

I did not change the sketch, neither did I change the pins.
Also did I check the pins like a trillion time, and ripped everything apart to use fresh cables and all that.

To check if the IDE might be faulty I tested it on my old grumpy PC laptop and got the same results. No connection at all.
With none of the 4 modules that worked the day before.

Is there anything I missed here?

This is where I got my sketch from (in german admittedly):
https://arduino-projekte.webnode.at/meine-projekte/parametrieren-des-hc-12/

It's too long to post here.

Maybe someone has an idea what might be wrong. I don't get it.

Thanks.

Cheers

Problem solved.

After measuring the Pins I realized that the description on the PCBs is wrong. They have mixed up RX and TX.

With a simple LED soldered to a resistor and two cables I tested 5V, GND, TX and RX.

Simple answer, TX and RX is printed wrongly on PCB.

Conclusion: Never trust what some lunatic wrote on a PCB. Always check. Might have saved me half a day.

I do not understand it. The day before it works and after some days rx and tx is printed wrong? Could it be, that you forgot to cross out rx and tx?