Most common issue is power supply. When a board isn't designed to be flashed this way, voltage may leak to other components on the mainboard. Hence board-specific documentation is so important. Measuring voltage when trying to access the flash may give a clue.

I'd read that can happen on some boards but was hesitant to try to program the chip with mains power connected. I don't want an $800 paperweight.

Without documentation it's best not to apply voltage via the flash programmer (RPi in your case), in case you were trying this. Better is to use the board's regular power supply and making sure that it doesn't boot (i.e. stays in a soft-off / S5 state). And *not* connec- ting VCC to pin8. Again, measuring voltage at the flash chip.

That makes sense. I'll give that a try.

That it's a WSON chip also doesn't make things easy. Did you solder something and can confirm connectivity? or how do you connect to the flash chip?

Ah. I didn't know what WSON was until just now. I have been using a regular SOIC clip. No I haven't soldered anything. I'm not sure how I will confirm connectivity other than by reading the chip. It looks like I may need a special probe to interface with it though.