Fixed power supply is quite big. I have set it to 10 V which are reduced by the energy management on the mainboard to the 4 V required by the SIM7600E.
Imax I have limited to 15000 mA. The solar powered setup is using two 3.200 mA Li-Ion batteries, so insufficient power should not be a problem.
Anyway - I will test the system with the batteries to make sure there is nothing wrong with my power supply unit (built this myself 30 years ago...).
Pin A2 is connected to the level converter of the SIM7600E.
It connects to A2 and then distributes to the upper 1K resistor and the diode IN5818 above it.
I switched on enhanced debugging as you suggested, however, the serial monitor ouput is the same. Is there any other place where I can see the enhanced debugging?
Will find out about the SMS test as soon as I can - next two days travelling. Can it be done with AT+CMGS directly when connecting the SIM7600E via USB, or do I need a sketch for this?
Thanks for all your suggestions so far!