If you can confirm the chip can be read correctly, then you need check the Vpp if any problem (you need use the Test H/W page).
You also can write the chip more than onece. If the byte can be write in this case, most likely the problem is the Vpp or Vcc issue. That means this chip is sensitive to Vpp/Vcc when programming. You may need adjust the Vpp/Vcc value a bit.