Hello everyone!
At first, yes I know it is not exactly HA related problem, but I know there are several people with successful setups so it would be nice to hear some comments and ideas.
I’m trying to set up a relatively simple configuration: an ESP32 DevKit v4 running Tasmota, with 3 units of PZEM-004 v3 connected to it. I’m trying to keep everything as straightforward as possible. The wiring is done according to this diagram. Everything is electrically correct—I’ve tested it with a multimeter. The PZEMs work correctly when connected to a PC via a UART-USB adapter. However, in Tasmota, I only see zeros, and after booting, it initially detects four units but then reduces the number to just one. On all 3 PZEM devices, I can see the RX LED blinking about once a second, but the TX LED never blinks.
Any ideas on what might be wrong and how I can get this working?
Thanks! 
Working through this now myself. I think you need to make a modification to the PZEM to drop the TX to 3.3V