The Danes clinched their ticket after August Holmgren defeated Elliot Benchetrit in two sets 6-2, 6-0.
Earlier, the Moroccan duo of Lamine Ouhab and Elliot Benchetrit lost 4-6, 4-6 to Denmark's Christian Sigsgaard Petersen and Frederik Nielsen.
On Saturday, the two teams tied 1-1 after Ouahab (813th in the world) lost to August Holmgren and Benchetrit (345th in the ATP rankings) defeated Christian Sigsgaard Petersen (969th).