There is a way to get around that constant pop up to link the account.
For the 1st pop up to link the account on starting the game, click cancel and click OK on the pop up window "Unknown error",
on the 2nd pop up to link the account, click OUTSIDE of the pop up window "Unknown error"
then the pop up to link the account will not happen again
However, you still need to repeat above everytime you start a new game