A: This means that either the customer is inactive in Fortnox - if that is not the case the most typical thing is that the user you have logged in with in the Fortnox app in Upsales does not have the accesses needed. Example of this is that the user does not have access to the customer register in Fortnox.
Then you need to logout from the Fortnox app and connect with a user that has full access to the different modules in Fortnox.