RFID-RC522 Can't access sector after writing to trailer block

Hello,
I'm currently using an Arduino uno r3 and an RFID-RC522 with GitHub - miguelbalboa/rfid: Arduino RFID Library for MFRC522 .

I wrote the following bytes to the trailer block in order to experiment with it:

byte writeBlockContent[blockSize] = { 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0xFF, 0x7, 0x80, 0x69, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFA };

I wanted to change the default MFRC522::MIFARE_Key key.keyByte and leave everything unchanged but I cannot access the sector anymore.