How to Solve Xhorse App Combine Dolphin XP005L "error: nation-code"?

One customer asked what is the nation-code error on Xhorse app. He was going to combine his Xhorse XP005L Machine but app gave this error.
combine device

Here is the Solution:
1.Login in Xhorse app first, then scan QR code to combine machine
2.If account is already entered, logout and login, and try again
link account