Strange.
As stated the gigabyte fibre internet was connected as I have video from the Ring video cameras for the same period, and the inverter is only 3 metres away from the router.
Plus the GivEnergy battery inverter was connected and hour and a half later when I noticed the problem and used the app to start the charge period.
I'll be watching closely in half an hour's time to see that it works for the 22:00 to 24:00 charge slot.