Unable to upload Web Server sketch to ESP8266 Thing (Invalid Head of Packet)

Hello,

I am getting a fatal warning and error while uploading the Web Server example to the board.

I have set it up as “Generic ESP8266 Module”, Upload Speed of 115200. I am running Windows 10 and had not experienced this issue with other examples. I have two boards and two cables and tried all combinations with same mistake, so it is probably not hardware related. I also tried to hold the boot button while loading but that just times out.

WARNING: Detected crystal freq 13.31MHz is quite different to normalized freq 26MHz. Unsupported crystal in use?

Crystal is 26MHz

esptool.FatalError: Invalid head of packet (0x46)

Any help will be highly appreciated. Trying to finish a sub-system for school here.

Best!