I just tried adding keep-alive. That didn't help. But I have tried something else and have got it to work.
The older post from March had a clue with the curl response that said there was
This is a problem with newer ESP8266WebServer's chunking interacting with IoTaWatt's older implementation. Never bothered browsers but I'll get it fixed in a day or so. After reading through the various releases of ESP8266WebServer, it looks like they have changed it yet again but that version is not yet published to PlatformIO, so I will need to understand the implications of that.
Thanks for your efforts. I'll post back when I have resolved on my end.
It's been interesting to explore Node-Red and I think you'll be seeing more of me in the future. Nice project.
