OH and Amazon Echo (Alexa) communications issue

Up until recently my OH implementation was working pretty well with Amazon echo (aka Alexa), however in the last couple of days alexa seems to has lost all contact with OH and all the devices are unresponsive. The devices are still controllable via the OH interface. Any ideas of where to start looking.
thanks Steve
ps. I deleted all the devices from the alexa app and tried to rediscover them, but the discovery failed for all OH devices.