Just got my 4.4.4 (KTU84P) update yesterday and the voicemail notification icon now shows up. Looks like this update fixed it.
My VM are working fine. I'm using the Google Voice app integrated with Sprint. Remember that this is a Google phone first not a Sprint phone.
Is really disappointing to still have this issue that was supposed to be fixed on the next release (4.4.3) i just got 4.4.4 but still no voicemail notification and support is been unable to fix it. I'm staring to give up with sprint my son prepaid phone gets better service and is cheaper what's the point of having a contract.
We had two previous known issues with the VM indicator: the indicator not going away and it not showing up. Both were reportedly resolved with the last update, build KOT49H. If that's not the case with you we'd like to get more information and report it back to our tech folks.
Sprint Social Care Team