Price update not working

Hello WordPress Members,

I tried updating the price only but somehow it is skipping all products.

Import settings:

• {artikelnummer[1]}
• {price[1]}
• {saleprice[1]}
• Custom Fields: name: _sku / value {artikelnummer[1]}

Import settings

• Unique Identifier: {artikelnummer[1]}
• Update existing producten with the data in your file
• Choose which data to update
• Custom Fields
• Update only these Custom Fields, leave the rest alone
• _regular_price, _sale_price and _price

Start import and all products are being skipped.
What am I doing wrong here ?