The website had logged hundreds of reports about the issue with the speakers, which are powered by Amazon's voice-controlled assistant Alexa. The reports started surfacing at about 8 am UK time on Wednesday.
"This morning we had an issue that impacted some Alexa customers' ability to interact with the service. The Alexa service is now operating normally," Amazon said in a statement.
Users from the UK and Europe had earlier reported widespread difficulty in connecting to the server.
On Downdetector, one user wrote, "I have three Amazon Echos, one Echo spot and two Amazon Echo dots (2nd gen) all glow with a red ring and are giving me the same message 'sorry, I'm having trouble understanding right now, please try a little later'"
Another said: "The Alexa app on my phone is showing "Sorry, we're experiencing system issues", and it says they're working on the problem."
Amazon did not respond to emails and phone calls from Reuters requesting more details on the nature of the problem.
A third user said: "Spoken with Amazon. They are having major server outages and are trying to resolve asap. I notice the Alexa in the Amazon Music app is working, but not on the Dot and Echo devices."
The problem also prompted a flurry of tweets with the #Alexadown hashtag.
Assuring customers of Alexa's security is crucial to Amazon, which has ambitions for Alexa to be ubiquitous - whether dimming the lights for customers, playing music or placing orders for them with the world's largest online retailer.
Alexa ran into trouble in May when an Echo device recorded a private conversation among an Oregon family and sent it to one of their contacts randomly.
In March users reported hearing unprompted laughter from their Alexa-enabled devices.
Amazon had acknowledged both these events and said fixes had been applied.
© Thomson Reuters 2018