So it had to happen - I lost connection with the Smappee servers late yesterday morning for no apparent reason.. It looks like the initial connect is failing and I can't figure out why.
I thought it might be something to do with the 5-year expiry of free access before you have to subscribe (at 2.5 euros a month).
However, what is odd is that I have an account at pvoutput.org and the live smappee data is still being uploaded there from the Smappee servers.
Anyway, while searching for solutions, I discovered it is possible to access this aggregate data locally directly from theSmappee hardware via MQTT.
Thanks to @AndyVirus, I was already picking up the real time data from the Smappee. I have now discovered it is possible to get the 5-minute aggregated data through the same mechanism.
This is a round about way of saying that I will be urgently commencing work on Version 4 of the Smappee plugin which will use MQTT to get the data and therefore avoid having to go out on the internet to retrieve it. I plan to store the five minute aggregated values in a Postgres database and use a similar device mechanism as is currently done.
I'll keep this forum thread posted.