The 1.2.22 firmware was updated to my hub today which resolved the problem. The button can now silence the hub alarm using a "then" command. Many thanks everyone, excellent! As an extra bonus one of...

Wayne-TP who works for tp-link has said It's fixed in a firmware update 1.2.22 for the hub in post #8 of this thread above, it's being released in stages at the moment. You can check your Tapo app...

@Wayne-TP Thank you, that is great news. I'll post when the update has come my way!

@R1CKW A beta firmware has been made which I am waiting to be sent for testing before public release to fix this. You could pm Wayne-TP to ask if you could be included in the beta firmware testing or...

Thank you Wayne-TP for the below PM from LA1's thread Re:H200 does not stop ringing after "closed and triggered" rules @Larok @LA1 The problem has been reported to the support engineer, i'll update...

Hello the become silent "then command" on an automation for the H200 hub to stop alarm ringing is not working. This is the same issue as LA1's thread with the title "H200 does not stop ringing after...