The diocese of Vannida (in Latin: Dioecesis Vannidensis) is a suppressed and titular See of the Roman Catholic Church. It was centered on the ancient Roman Town of Vannida, in what is today Algeria, is an ancient episcopal seat of the Roman province of Mauritania Cesariense.
The town of Vannida was located in what is now an African country.
It's definitely correct because it says it is located in what is now Algeria, and Algeria is an African country.  I think the system might not understand such a complex question and be able to understand what it means for a country to be an African country perhaps.