Hi @Wayne_
Welcome to the community forums.
Sorry to hear that you're having issues with your WiFi and connecting your devices further away. I have check the system at our side and cannot see any area concerns, or issues with your power levels at all.
What I have seen is that your 2.4 band isn't on the best channel, we would normally recommend channels 1, 6 or 11. The reason for this could be that you have turned off channel optimization and have made changes to your WiFi network settings.
I recommend performing a 60 second pin hole reset on the router. This will revert any customisations back to factory settings and full update the router with firmware/software updates. Please do not reboot the router whilst it is completing the pin hole request.
Once this is completed, without changing any settings, please try the connect app in the room where you are experiencing the issue. You can also perform a speed test in any rooms you find blackspots.
When you're in the room where the issues are, does the device pick up the WiFi signal at all or does the connection slow/drop outs intermittently?
Please can you run a Sam Knows speed test on a PC / Laptop / SmartPhone / Tablet from the room(s) you're experiencing speed issues in and let me know the results. When you run the checks, please ensure you do not have a VPN enabled or have other devices actively using the internet connection at the time of the test i.e streaming / downloading / gaming etc