BTN2 not working, even after updating firmware

Did you install something other than the default app? It might be there is an issue with one of the clock apps - if you could let me know which one I can see if I can reproduce/fix it here.

However, all you need to do to get it working is: https://www.espruino.com/Bangle.js#resetting-without-loading-any-code

• Long-press BTN1 + BTN2 for about 6 seconds until the screen goes blank
  
• Release BTN2 but keep pressing BTN1 while ==== goes across the screen
  
• Keep holding BTN1 while Bangle.js boots
  
• Release it - you should have the Bangle.js logo, version, and MAC address
  
  

So you go through the bootloader, and as long as it boots with BTN1 held down, it won't load any of your saved code. You can then connect with the App Loader and remove the offending clock app and/or try 'Install Default Apps' which is basically a factory reset.