There is a google play support thread that so far leads to no where, but it seems like a general issue with many people from many different countries reporting the same thing (including myself).
It seems that some people have managed to make it work by using a phone number from another country, specifically a "developed country".
Just to make sure, here's Google support recommendations for this issue:
- Enter your phone number in a valid international format:
Format: +(Country code)(Area code)(Phone number) Examples: +14155552671, +441234567890
- Try both verification methods: text message or voice call.
- Using a fixed-line phone if you’ve been using a mobile phone, or vice versa.
- Ensure you can receive calls or texts from others.
- Make sure your mobile phone has a strong signal.
- Try verifying on another day or wait 24 - 72 hours between tries.
- Try a different supported carrier.
- Reset cache/cookies or Use an incognito window.
If nothing of the above works, I recommend to create a support ticket to get their attention.
UPDATE:
As I have validated @Abdelhakim's answer: The issue we initially encounter is a temporary error (400 - "Precondition Check Failed" when viewed through the browser console). After multiple attempts, we start receiving the 429 - "Too Many Requests" error. At this point, the only option is to wait for the system to reset, as it will continue showing the same error no matter what phone number you use. For some users, this reset occurs after one day, while for others, it may take 10 days or even longer. It is advisable to be patient and avoid further attempts, as each attempt might reset the timer.
If you encounter the 400 error, stop immediately and consider the original advice to use a phone number from another country, particularly from a "developed country" to try again. It is also preferable to choose the call option over SMS.
If you have waited 10 to 15 days and continue to receive the 429 error, as the validation deadline (including extension) is approaching, you might consider, as a last resort, creating a new account and transferring your apps to it. Use the same strategy to validate the new account. This is the course of action I am preparing to take, as I am now less than a month away from my deadline.