Hello, does anyone know on how to resolved this error on csv import of new customer. "You can add a subsidiary to an entity only when you have access to the subsidiary."

Sounds like the role you're using to do the CSV import doesn't have access/permissions to the subsidiary you're trying to set for the customer record(s)

View permission on subsidiary record already given on the role being used but still same error

Is the user able to create a new customer to that Subsidiary through UI? If no it’s permissions.

yes can create via UI using the same role used on CSV import

How are you specifying the subsidiary in the CSV? What's the setting on "Include Children"?