SoundLink Color 2 disconnects while updating from 2.5.1 to 3.0.3
I have never updated my Bose Soundlink Color 2. But since I am facing the universally known issue of "speaker not charging/powering up after full discharge", I thought to update my firmware as there is no other option left. The 15 sec hold power/multifunction button solution didn't work. It just blinks the power amber light twice. So I tried everything mentioned here -https://community.bose.com/t5/Portable/Bose-Soundlink-Color-II-not-charging-no-power-flashing-lights.... Again no luck.
Now when I am trying to update the firmware from 2.5.1 to latest 3.0.3, I am getting this connection error- "We lost connection to your product. Try unplugging your product then plugging it back in." although my speaker is firmly connected to the PC via Bose USB. I have tried with both Win and iMac updater, same issue. Can someone help? Is the version gap too much for an upgrade (but then it should not "disconnect" while updating, right?), if so, can someone provide me intermediate versions that are update-able?
I am blocked completely, no more explore-worthy options left (except this post).