Sona's passive currently has a bug in which if another ability is used immediately after her power chord is used her passive will not stack. It's shown in the video linked where a q power chord is used and W is immediately pressed after. She gets the move speed buff from Celerity, however, it shows her at 0 passive stacks. I was only able to recreate it when I had 20% CDR.
Hopefully this helps! 
Vesarixx1 votesGuess I'm not crazy, kept noticing this when I was spamming Sona mid
RedCyclone1 votesBeen there ever since her damn rework
kept trying to get them to fix it before giving up im sure they will make sure to keep her Q aura bug in too
Riot don't give a crap about Sona
XeroKimo1 votesThere's also a bug with her Q tho it's very tiny and isn't that harmful, if you start off with Q at level 1, the very first time you use the Q, the empowered AA is on for the whole duration, I've noticed this happening twice when I leashed my jungler
