I was having problems reading some Microchip eeproms in an old Panasonic phone. Newer phones had similar eeproms and I could read and write fine but the old ones would read all 0s (not blank FFFF) and blank check would fail… could not write (program) and verify would fail.

93LC46BX
93LC66BX

I thought maybe my Minipro programmer was broken so I ordered a cheap EZP2019+ but that had the same issue

I could read / write / verify the 93C56W with no problems on both programmers!

After many hours searching on google I never did find a similar issue or explanation that would help me figure out what I needed to do. But at my last glance at a datasheet I saw this little note:

ROTATED SOIC
(ex: 93LC46BX)

ROTATED IC?!?
AH-HA!!

A little barely mentioned fact that some 93LCxx eeproms have a rotated pinout!

I had tried setting my programmer to 93LC46B (BX was not available) and thought that would be the closest match.
NOPE! But when I selected 93LC46X THEN the programmer would read and write to the IC.

So maybe this will show up for someone else searching google for an answer. If you cannot read a Microchip eeprom 93LC46 or 93LC56 or 93LC66, etc… maybe try the rotated pinout option in your programmer (part number ending in X on my Minipro programmer)

If you don’t have the option of selecting a rotated IC in your programmer you could make or buy an adapter