The other day I noticed my Amazon Echo dot blinking and pulsing yellow light ring. So I came across this official page that explains the different types of light rings and their meaning. According to the page, the yellow blinking light ring means
A message or notification is waiting for you. Say, “Play my messages” or “What are my notifications?”
I tried to read my notifications by saying above commands but still, the yellow light did not disappear and Alexa said there are no messages or notifications. So opened my Alexa app on the phone, to see if I can manually delete or read the notification but no it did not help and I cannot see any notifications or messages.
I finally said this command and
Alexa! Delete all my notifications
voila the ring did not appear anymore.