No heating thrmo not firing boiler

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I have no idea why but last week we realised the heating wasn't coming o, did some checks and the wireles throat is recording the right temp checking the app it's recognising that the temp is low and says the heating is on the wired controller is showing the heating is on but it will not fire the boiler,,,, the hot water on the other hand fires up right away

Any ideas what's going on IV tried resetting everything IV tried re installing everything turning the boiler of complexity some people have suggested the 3way valve but this has been replaced
Any help would be much appreciated the kids are cold and won't stop telling me