"Sorry, you can’t enroll at this time."

Quoting the Apple Developer Agreement:

1. Relationship With Apple; Apple ID and Password. You understand and agree that by registering with Apple to become an Apple Developer (“Apple Developer”), no legal partnership or agency relationship is created between you and Apple. You agree not to represent otherwise. You also certify that you are at least thirteen years of age and you represent that you are legally permitted to register as an Apple Developer. This Agreement is void where prohibited by law and the right to register as an Apple Developer is not granted in such jurisdictions. Unless otherwise agreed or permitted by Apple in writing, you cannot share or transfer any benefits you receive from Apple in connection with being an Apple Developer. The Apple ID and password you use to log into your Apple Developer account cannot be shared in any way or with anyone. You are responsible for maintaining the confidentiality of your Apple ID and password and for any activity in connection with your account.

The part about 'legally permitted' means you are of legal age to enter into a contract as defined by your country.

18, as an example, is the legal age for California, USA, where Apple is headquartered - earlier agreements used to use that number, where the legalese has been made more global since, in order to accomodate legal age requirements that can differ from locale to locale.

Some younger devs have a parent/legal guadian buy the dev account, and then when they are of legal age, they buy their own account and transfer their apps over to it.

Keep in mind that the account owner assumes all legal responsibiity, including any tax burden that results from store revenue.

Good luck.

i have same problem to, another issue is country / region.