Just to rule it out as a possibility, can you uninstall that profile, do some testing, then reinstall it?

I used to have occasional issues with the profile I was forced to use at a former job, where it would block some traffic, seemingly randomly. I’m sure there was a reason, I just never could figure it out, and as you have suggested, I just lived with it. 
 

I’m more curious than anything else…completely understand if you feel it’s too much effort. 

Hiya,

just tried it and it made no difference

will just have to live with it

Dark mode is enabled by a feature-set definition stored in the cloud. If the server is unreachable (or offline obviously) it may not work. A DNS filter could be a possible culprit. 

I have tried 3 different DNS services, Google, CloudFare and NextDNS…. All behave the same way.

Also, my wife is in the same network with the same DNS servers and it works fine for her.

really strange 

Reset your controller and reconnect it to the ‘existing system’ when it restarts. 

Tried that several times, just tried it again….. no difference 

Did you try rebooting your mobile? 

Yes, rebooted phone many times … everything has been rebooted during tests.

Maybe reset the iPhone’s network settings and then setup the WiFi connection again. 

Hi Ken, as it is on both iPhone and iPad, unlikely to be that.

Will have to see how that is handled these days, I think it has improved, but it used to a fairly nuclear option that took ages to get things back.

It just resets the network/WiFi settings to factory - you would just need to setup the WiFi connection again. However I agree, if it’s happening on two devices that it may not be the answer, but strange it works fine on some devices on the same WiFi network, which infers it’s something related to the iOS device.