I thought I did the same but I was still able to write to it. Are you totally unable to write? The NExT product page says (if you scroll down and expand “NTAG Chip Security”)
Regardless of what some NFC smartphone apps indicate, it is not possible to remove or disable the password, it is only possible to set the password to the factory default hexadecimal value of 0xFF 0xFF 0xFF 0xFF. If the password is not changed, and is set to the factory default, then anyone could easily authenticate, change your password, then write data or change protection options for your chip implant to lock you out of your own chip. Because of this, we set a default password value of 0x44 0x4E 0x47 0x52 which is ASCII code for DNGR (some older batches of NExT chips have the password 0x4E 0x45 0x78 0x54 which is the ASCII code for NExT).