The tech giant didn't respond to a request for comment.
Google said in April that it would. The search giant decided to focus resources on Rich Communications Services, or RCS, instead. RCS is designed to bring enhanced features to SMS texting.
Allo debuted in 2016 as a challenger to Apple's iMessage, Facebook Messenger, WhatsApp and other chat applications. The free app has been available on both Android and iOS devices and has featured Google's digital assistant that retrieves information for users in a conversational way. Allo also has end-to-end encryption and an incognito mode designed to erase messages.
The app is already down for many users, according to 9to5 Google. Messages reportedly can't go through, and the Google Assistant in the app apparently doesn't work either.