Ensure endpoint URLs match your production domain exactly.

Validate whether the flow is opened from LINE app or browser as designed.

Booking and member pages can use different LIFF IDs.

Use separate env vars such as NEXT_PUBLIC_LIFF_BOOKING_ID and NEXT_PUBLIC_LIFF_MEMBER_ID.

Verify LIFF ID in DB/ENV against the actual deployed LIFF app.

Verify rich menu URL format: https://liff.line.me/{LIFF_ID}?shop_key=...