google cloud platform – GCP GKE version mismatch between nodepool and nodes

I’ve an issue where the nodepool version on my gke cluster shows the same version as my control plane version but the nodes inside the nodepool are on an much older version , infact, they haven’t been recreated for close to a year. I’m now getting a critical warning , showing that the version skew has reached the maximum .Attempted a manual update but it already shows the latest version in the nodepool and so I am stuck . What could be the cause and how do I proceed ? I am a noob to gke so please help out 🙂