Default I can't get into cwm

I have followed the instructions, but every time it goes into factory reset prompt rather than cwm interface. 1.4.3 firmware, not rooted as far as I know. I have 4 nook tablets and 2 of them do this; 2 work when following the instructions. the ones that wont go into cwm seem to be otherwise functional.

edit: turns out two were 16gb and two were 8gb.

16gb = bntv250
8gb = bntv250a