Casted Ability Doesn't Cast Before Death - User Screen Shows It's On Cooldown Pinging it Says Ready

I wasn't able to capture this in replay super well because it concerns the spell overlay. Scenario was that I was playing Sona and I casted her R. On my screen I got the audio for the ability and saw the animation, but then I died almost at the same time. The opponents were not affected by the ability and my lovely team pinged me to show that my R was ready. On my screen R was on cooldown and I was unable to cast the spell. If I pinged the spell which showed the countdown timer, the ping said R - Ready. Not sure if this is just bad communication between server and client, but was rather frustrating.