【Updated: 】
You can link your Nintendo Account by following these steps.
■How to link
① Open Animal Crossing: Pocket Camp.
② Tap Transfer Save Data.
③ Tap Create/Link Nintendo Account.
④ Register your Nintendo Account.
If this did not resolve your issue, you can also refer to these articles.
- What is a Nintendo Account?
- I want to transfer my current save data to another smart device.
- I want to create a Nintendo Account.
- Can I change or unlink the Nintendo Account that I currently have linked?