Home Kit Automation Suddenly Not Working

Hi

I've posted this under Home Pod as it's about Home Kit and I can't find a forum for that, so if I'm in the wrong place please tell me and I'll move to the right forum.

I've had an automation running for months, turning my lights on at sunset and off at a set time. But now it has stopped working. I have location services for the HK enabled and haven't changed anything. I can control the lights with the app, and when I use 'test this automation' it works, but just not in real time. Additionally, one of the lights is sometimes unresponsive for no apparent reason - again it has been working perfectly until now. I've unplugged everything, quit HK and tried again, but still no success. I tried changing the automation slightly but that didn't make any difference either. Does anyone have a solution to this? The lights are on a Philips Hue bridge and connected to the same network as my phone (not that this should make a difference).

Thanks

WG