Own GTIN is not unique...
Error:
The own GTIN is not unique. It was used first in the import file for the article in question.
Explanation:
Your own GTIN is not unique. It was used first in the import file for the article in question.
Solution:
Each article must have a unique GTIN. Find the double GTIN numbers and correct them so that there are no more double GTIN numbers in the import file.