I have various door sensors which trigger my downstairs Tapo hub to ring when the doors are opened.

I have a second Tapo hub upstairs which is triggered to ring when the downstairs Tapo hub rings. 
This has all been working perfectly but suddenly the upstairs hub has stop ringing when the downstairs hub rings when door sensors are triggered.

if I trigger the downstairs hub to ring manually via the Tapo app (I.e not by activating a sensor) the upstairs tapo hub will ring.

Any ideas as to why the smart automation has stopped working for the upstairs hub when the door sensors are triggered?