In this app, only one play data can be linked to one Apple ID or one Google account.
If you see this message, the Apple ID or Google account you are attempting to link may be still linked to your previous play data. In this case, your current play data cannot be linked to the account.
Example:
You linked Play Data A to Google Account A.
After that, you deleted Play Data A, and newly started your play with Paly Data B.
Note: In this case, Play Data B cannot be linked to Google Account A, because simply deleting Play Data does not unlink it from the account.
Solution ①
If you have another Apple ID or Google account that is not yet linked to "Atelier Resleriana: Forgotten Alchemy and the Polar Night Liberator", please consider linking the play data to that account.
You may also create a new Apple ID or Google account to link the data to that account.
As one play data can be linked to one Apple ID or one Google account, the data can be linked to another un-linked Apple ID or Google account.
How to create an Apple ID:
https://support.apple.com/en-us/HT204316
How to create a Google account:
https://support.google.com/accounts/answer/27441?hl=en
Solution ② *This requires contacting Customer Support.
If you cannot try the above "solution ①" for some reasons, such as you do not have another Apple ID/Google account, please contact customer support from in-game "menu" >"Contact".
How to prevent this situation from occurring?
Before deleting your save data, please Unlink Account from the data you wish to delete.
To unlink account, please follow the steps below.
Go to the in-game "Menu" > "Link Account" > "Sign in with Apple" or "Sign in with Google" > "Unlink".
*This operation unlinks the data, and the originally linked play data will no longer be recoverable.
Example:
You linked Play Data A to Google Account A.
After unlinking Play Data A from Google Account A, you deleted Play Data A.
Then, newly started your play with Play Data B, and linked Play Data B to Google Account A.
Note: In this case, Play Data A cannot be recovered because it was unlinked from the account.