A: The full message is Misslyckad överföring. Den anslutna kunden är inaktiv i Fortnox. Aktivera kunden i Fortnox innan du stänger affären i Upsales. It means that the Fortnox customer linked to the account on the order is inactive in Fortnox, so the order can't be exported.
The linked customer is the one whose customer number is in the account's Kundnummer field in Upsales. The check runs when you save the order in the stage the Fortnox app exports.
To fix it, find that customer number in Fortnox, activate the customer there, and save the order in Upsales again.