error message: "can't verify device number 1"

Hello Dan,

unfortunately I can't see from a distance what's going on in your circuit, and may be, I would have the same difficulties with the circuit at my fingetrtips.

delayed was referring to the fact, that the error occured after several programming cycles, if I understood right. To verify, that the design isn't damaging the flash by excessive write or erasure requests, I would disconnect the respective control lines and try with a new device.

If this kind of design problems can be excluded, I would return to possible hardware issues. There must be something specific to your present hardware.

Of course, individual parts may be defective, respectively have been damaged by solder/desolder or ESD events. So it may be misleading to base the conclusions on the behaviour of a single part.

Regards,

Frank