[Solved] Trouble performing BLE DFU update on Bangle.js

Oh, OK, you previously said

I can see "DfuTarg" bluetooth device in my bluetooth discovery app (laptop and mobile)."

So you see it on laptop but not on phone? So it may also be something with your phone or nrfToolbox, not just the watch. So maybe just try again, toggle bluetooth, put the watch near the phone, restart phone, go to more radio quiet place or maybe try nrfconnect instead, but that one is maybe harder to use. If you see DfuTarg in the list click connect and there should be DFU icon in top right corner.