Welcome, Peter, to the OEM forum.
I do not have access to the records from the shop. I have asked the question for you.
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It appears that you have the 3-phase sketch, but the standard software in your ESP. That will explain why it is not communicating.
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That is correct. The 3-phase sketch will give a good estimate of real power (Wirkleistung), the standard sketch will give the incorrect values for real power, but it does calculate - but not show - apparent power (Scheinleistung) correctly.
I am sorry, but I cannot answer this. I do not have an ESP8266 module, therefore I have no experience of this.
Because the emonTx is very busy when running the 3-phase sketch, it is not possible for it to communicate with the ESP8266 module at the default baud rate. It therefore needs the baud rate in the ESP8266 to be reduced to 9600 baud.
It is always good to have this adapter (“programmer”). If you do obtain one, be warned that some do not work with our system. If you buy from the OEM shop, that one is guaranteed to work.
If you do buy the programmer, you can adjust and load the 3-phase sketch in your emonTx, and calibrate it for your system if necessary, and you can load the software for the ESP8266 that has the correct baud rate:(https://community.openenergymonitor.org/uploads/short-url/zegtvp5lICQT1w6J7ZoTXRnsiw3.bin)
If you download the 3-phase sketch Update to 3-Phase PLL sketch - #15 by Robert.Wall
then you must read the documentation that comes with it, and choose the options that are right or you. (I’m sorry it is in English only - your English is much better than my German.)
I wrote the sketch for a fellow countryman of yours, @Simsala. He uses the 3-phase sketch and emonESP and he might be able to help you.