MIC mismatch error is usually caused by the APPKEY.
I suggest you try to generate a new APPKEY and use that on your RAK3172. You can generate a new one under Join Settings in the General Settings tab of your TTN device console
There seems to be that bug that joining is possible only after rebooting the module after setting the APPKEY. That’s somehow annoying but NEVERTHELESS it WORKS that way! I could not find any hint on that in the documentation. Thank you for the advice. I assume this will be the cause of many problems or seemingly erratic behaviour.
Good thing it works. We have new RAK3172 FW that is based on RUI3. I never experience this issue anymore. I suggest you update your firmware and see if things will improve.
There are minor differences on the old RAK3172 FW and the RUI3 though.
Please follow this DFU guide. The links are updated and will send you to the right links.
The updated RAK3172 FW is now based on RUI3.
RUI3 is a firmware platform we created so we can unify the firmware of our devices regardless of chipsets. Also, it allows you to compile firmware directly on the device and not relying on the AT commands and external host MCU.