Pico: Bootloader mode, than not connected

Actually this could be something else. I believe the Pico you have is one of the first batch that were made 6 years ago (it has a sticker on the STM32, subsequent ones didn't).

Something changed in the Windows 10 OS drivers, and I believe it meant that the Pico's bootloader no longer got detected in Windows 10 properly (or maybe w10 does treat it as a modem?), even though the Pico itself works fine when booting normally.

So you have two options:

• Find another computer and update from there. I believe Windows 7 works fine, or MacOS will work
  
• Probably the best solution here is to use 'Advanced Reflash' instructions here: http://www.espruino.com/Pico#advanced-re­flashing
  
  

'Advanced Reflash' is a bit more of a faff, but it should fix your Pico for good, and you can then easily update with the IDE from Windows 10 from then on.