Lots of reports users locked out of accounts due to 2FA codes not being sent, error appears wrong ( We cannot send a text message to this phone number because its operator is not supported) as Twitter is not even firing the code. UK and India users mainly surfacing for problem.
https://twitter.com/search?q=%20We%20cannot%20send%20a%20text%20message%20to%20this%20phone%20number%20because%20its%20operator%20is%20not%20supported&src=recent_search_click&f=live
Do NOT reset passwords without removing phone first or you will be logged out totally without a way in.