https://www.allaboutcircuits.com/uploads/articles/20170323-lee-wifieye-circuit-pgm-1.jpg
Are changes necessary to permit SPIFFS upload to flash?
See here https://github.com/esp8266/Arduino/issues/4061
Maybe this is also your problem...
schufti wrote:Recently there are reports of modules with incompatible flash memory chips marked "puya"
See here https://github.com/esp8266/Arduino/issues/4061
Maybe this is also your problem...
Thank you for your thoughtful reply, Schufti. That thread seems to be concerned soly with the esp-01. I'm using an 8266-f. I suppose it is possible that the flash chip under the shield is a Puya. I will try to run some of the diagnostic scripts that have appeared in that thread. Would you happen to know how to get the esp to report the names of chip manufacturer used for flash?