One of my three Echo Dots had been mothballed and I dug it out this afternoon to assist with my testing.
It had Firmware= 608490720 which obviously was well out of date.
So I forced a Firmware update. I think you can tell Alexa to do it but I just held the microphone disable button down for thirty seconds until the red ring went off and released the button when the blue ring appeared. It updated the firmware to 641575220. That was late this afternoon.
It could be of course that there is different firmware for different regions?