Thank you very much for your interest in our products.
Depending on the previous configuration that the tag has, it can or cannot be written with an NDEF. In case you are trying to save an NDEF message, you can do so by entering the TagWritter App. In the main menu, please click on the Erase option (down left button), the second option; Erase, and format to NDEF.
I hope this information may have been useful.
Best Regards,
Fabian