Is the region where ScanSnap accounts are not available selected for the region setting on the mobile device that you are using?
Even when you are in a region where ScanSnap accounts are available, if the region where ScanSnap accounts are not available is selected for the region setting on your mobile device, you cannot sign in to a ScanSnap account.
Change the region setting on the mobile device to the region that you selected when registering a ScanSnap account.
For details about how to change the region setting on the mobile device, refer to the manual of the mobile device.
Did you enter the ScanSnap account correctly?
ScanSnap accounts are case-sensitive.
Check that the ScanSnap account you entered is correct.
To sign in to a ScanSnap account with your social media account, tap the [Sign in with Google], [Sign in with Microsoft], or [Sign in with Apple] button and enter the required information in the window that appears.
Is a message displayed, indicating that a ScanSnap account using the specified e-mail address already exists?
The e-mail address previously used to sign in with a ScanSnap account or social media account cannot be used as the e-mail address for signing in with a different account.
Tap → [Account] → [Account management page] in ScanSnap Home and sign in again with the ScanSnap account or social media account you previously used to sign in with.