It's not just cycles. So many factors like heat and how the battery was used effect it's life. Was it kept at 100% or 0% for extended periods. Also 2016 was 7 years ago. I don't know when your model was made but lithium batteries don't last forever.
Other reasons are:
-- bad charger/psu;
-- unsieved voltage drops;
-- heat;
-- bad battery itself, common story for (not all) unauthorized service centers