We're sorry to hear that you are having issues joining the developer program. We're also updating the error message to be more specific.
We recently had some service issues and many countries were temporarily blocked from joining. This issue has resolved but note the following: Geographic limitations. For technical and security reasons, the Microsoft 365 Developer Program only supports a subset of countries/regions listed here: Microsoft 365 International Availability. We review our supported country list regularly. If you are unable to sign up from your country or region, then it means we do not support it at this time. Membership benefits
While you can still join the developer program, access to the free Microsoft 365 E5 subscription is currently paused for the short-term while we adjust the qualifications for that benefit. To stay apprised of changes, please follow our blog.