Q: tengo mi id apple y contraseña, pero no puedo activar mi iphone; ya cambiado clave y nada

Why was I asked to wait before setting up two-step verification?

As a basic security measure, Apple doesn't allow setup of two-step verification to proceed if significant changes were recently made to your Apple ID account information. Significant changes can include a password reset or new security questions. This waiting period helps Apple make sure that you are the only person accessing or modifying your account. While you are in this waiting period, you can continue using your account as usual with all Apple services and stores.

Apple will send an email to all the addresses you have on file notifying you of the waiting period and encouraging you to contact Apple Support if you think that someone else has unauthorized access to your account. You can set up two-step verification after the date listed on your Apple ID account page and in the email that you receive.

When your waiting period is over, you have 30 days to complete setup of two-step verification. If you attempt to complete setup after 30 days have passed, or you made significant changes to your account during that time, another waiting period may be triggered.

copied from Frequently asked questions about two-step verification for Apple ID - Apple Support

If you are still having problems, maybe you should contact Apple - Support - Apple ID