New installation. No entities show in HA

[TeamWetLettuce]

Firstly, thank you all so much for the many useful posts you people put up on here, FB and Youtube.
I am new to HA so please bare with me.
I have wired up 2 Waveshares and the connectors to a POE Hub as in this article. My dongle is a S3-WiFi-ST. Solis cloud still works fine on connecting via the new socket connected to the Waveshare slave. So that would potentially tell me that I have configured the Waveshares and the connections correctly.
I am at a bit of a loss as to what to do next. I have followed a Youtube (I think Gordon Markus who does something similar, but not identrical), and installed Solax Inverter Modbus via HACS, and then configured it in the Devices and Services. However it comes up with 0 Entities no matter how many times I try to do this. Have I missed another step? Are there any other tests I can do to check connections etc? Any thoughts please?

[TeamWetLettuce]

Well having tried so hard, I have re-installed angain and now find I have 146 entities. Thanks again everyone for all the documentation you provide.