We’re other users, and some here are third-party developers. Not people that work for Apple.
In no particular order…
If you have an add-on VPN client app in use, discontinue and remove that.
If you’re using the developer website to enroll, try enrolling via the developer app.
If you’re in India and using (trying) the website, you’ll need to use the app.
If you have a mobile number format Apple ID, those usually haven’t worked and an email-format was (is?) needed.
If you’re in an embargoed or restricted region or country, that enrollment won’t work.
If you’re a denied person, that enrollment won’t work.
If you’re in a country or region where Apple isn’t active, that probably won’t work.
If you can’t be reached via direct incoming international call, find a communications carrier that allows that.
You’ll need a major international payment card associated with your Apple ID.
Apple Gift Card and Apple ID balances won’t work for enrollments.
If one of those is not the case here…
Contact Apple Developer Support.