Last night my Kardia stopped working, I changed the battery and it still didn't work.
I did all the checks I could think of and still it did't work.
I considered buying a new one maybe a 6 lead and was looking at compatibility with my second hand Iphone and ancient Ipad and noticed a recent update of OS compatibility 17 days ago to 16.5 for me . Strangely my Kardia continued to work until now.
alivecor.zendesk.com/hc/en-...
I updated my OS today and the Kardia now works.
I don't have an automatic update turned on on my devices,I find them disruptive .
If your Kardia doesn't work today try checking check your OS for an update .