I have also tried flashing with Tasmota it also appeared to flash correctly but did not work. I finally flashed with the Sonoff bin file using ESPEasy instead of using the IDE Arduino. This worked fine, I was able to see the board on the network and program it using Tasmota .
Unfortunately Tasmota is not flexible enough for my needs. I need to be able to program it using the IDE Arduino development tools.
Any suggestions