Hi there!
- Check the list on the System Status page. If the box by iOS Device Activation isn't green, try to activate your iPhone later.
- If asked to enter your password as you activate your iPhone, enter the password. (A password prompt means that Activation Lock might be enabled in Find My iPhone.)
- Restart your iPhone.
- If you're using a cellular data connection, connect to a reliable Wi-Fi network instead.
If this doesn’t help, learn more things to try and how to activate via iTunes here: If you can't activate your iPhone - Apple Support or if you’d prefer to contact Apple Support, you can do so here: https://support.apple.com/