When using either the app or alexa my boiler fires up but goes off after 5mins

So iv just installed the v3 kit to my Main eco 30 all worked fine for 2days Alexa would turn off and on when requested the app was working fine, all of a sudden now when i ask Alexa to turn on heating the boiler fires up then goes off after 5mins
Then i have to use the app pull the slider all the way to 25degrees then the boiler may fire up i can hear the click on the receiver sending the signal it takes ages for the boiler to fire up or sometimes wont fire up i then have to reset the entire system then start all over and it will work again for a while then back to the same issues
Any suggestions as to whats causing this?