The service you have with us does not support LINE’s age verification service and so when signing up with Line, you will need to skip this step.
The only features that are not available when skipping age verification are the ID search and phone number search options.
Even if you are unable to use these search functions, you should be able to add your friends via friend addition or QR code. You can also add friends to LINE by synchronizing your phone address book with your LINE address book.