In the Enhanced content preferences chapter, under AmazonCoverImages (https://koha-community.org/manual/latest/en/html/enhancedcontentpreferences.html#amazoncoverimages) "based on the first ISBN number in the item’s MARC record" ISBN number -> ISBN (the N already stands for "number")
Same error under OPACAmazonCoverImages (https://koha-community.org/manual/latest/en/html/enhancedcontentpreferences.html#opacamazoncoverimages)