emonTx not sending CT data

I think you need to reflash the EmonTX. I’d be concerned about the serial output that is shown here as ?.

I did this successfully via the PIO method on a PiZero (I updated the docs), but you need the RTS line connected and change the pin number, else Robert’s way with a programmer and Arduino IDE.

[edit]
Also note if you use the PIO method, you need to install the library first. The docs were written with this line in the platformio.ini file

lib_deps_external =
  https://github.com/openenergymonitor/EmonLibCM.git

But @glyn.hudson changed it back to just EmonLibCM @2.4.1, but this means you need to install it manually rather than have the PIO package manager do it for you.