Account Hierarchy Error "Instance with the same key already exists"

Hi all,

We are trying to migratie customer hierarchies but when I try to run the "import simulation" we got the following error:

When I Click on the error I see following:

I opened this tab in Excel but I see nothing in this tab (I unhide this tab)

I enterd followin data in excel:

Can anyone tell me what I did wrong?

Thanks in advance!

Regards