What is happening: Users who have enabled two-factor authentication (2FA) reported not being able to log into their Twitter accounts on a new device.
"We cannot send a text message to this phone number because its operator is not supported," read the error message shown to these users who attempted to log in.
All signs indicate that 2FA is the point of failure.
While it is not clear when the issue first arose, some have been struggling to regain access to their accounts since last week.
Why it matters: "It's really bizarre to ask me to just make a new account because it's also a professional setback. I'm a freelance journalist and it impacts the reach of my stories," Srishti Jaswal, who has been locked out of her Twitter account since 13 December, told The Quint.
Radio silence: Jaswal also highlighted the lack of responsiveness from Twitter Support to help resolve the issue.
"I felt really alarmed and told some of my friends, they tweeted and asked Twitter Support to help but there has been no response from their side. I have again and again filled up those [contact] forms but then they said that they can't reopen my case because it's already decided. So, does that mean I've effectively lost my Twitter account?"Srishti Jaswal, freelance journalist
No way in: "I'm not even able to create a new account because it says that my phone number is not valid," said Sukanya Shantha, another affected journalist.
Workaround: Users can still unlock their accounts by using a device in which they're already logged in, to turn off 2FA.
Yes, but: Shantha and Jaswal are among several users who are not always logged into Twitter at multiple places.
In fact, Jaswal revealed that she chooses to sign in and sign out of Twitter every time in order to protect her mental health from addictive social media platforms.
What they're saying: "To clear up confusion about two-factor authentication on Twitter – it’s still live and a good way to protect your account. If you have it turned on, your chosen authentication method should be good to go," the Twitter Support team said.
"We’re looking into the few cases where SMS codes aren't being delivered," it added.
The big picture: Since Twitter has not provided any details about the failure of two-factor authentication on its platform, the only plausible explanation can be drawn from a recent report published by Platformer:
Twitter blocked major telecom service providers in India and Russia from sending SMS texts including 2FA codes to users, the report said citing internal communications.
The move was apparently not on purpose: Twitter was trying to get rid of spam at the behest of Elon Musk.
But instead of identifying specific users, the platform reportedly ended up blocking all traffic to and fro mobile networks with large spam networks.
However, Platformer also reported that the telcos were unblocked shortly thereafter. So, why is two-factor authentication still down? Is it isolated to India or are users in other countries similarly affected?
The Quint has reached out to Twitter as well as major telecom service providers in India and will update this report if we hear back.