Hello E Steures,
Please check your settings in FBZP - Paying Company Code -> Note to Payee by Origin.
If you have here the origin FI-AP, than the customizing above is relevant only for Vendors.
You have to create a new line FI-AR for Customers.
With an 'empty' line the Note to Payee will be called by all type of origin.
Please check also the F1-Help of the field 'Origin Indicator' for more details.
Regards,
Emoke