Should I be manually re-applying the manifest for this? My cluster is currently down due to this problem

How did you create the CNI in the first place? If you didn't specify a way to manage it, then EKS just creates it, but doesn't manage it or update it. (thanks EKS) Looks like Pulumi provides a resource for this: https://www.pulumi.com/registry/packages/eks/api-docs/vpccni/

So I used

new eks.Cluster

to provision my eks nearly a year ago - and if eks creates this, wouldn’t it create problems to also create it via pulumi’s vpccni resource? What do you suggest? Should I just update it manually?

honestly not sure, I haven’t used the pulumi resource myself yet. Updating manually is probably safe to get you un-stuck. You can always import later

OK that’s what I thought - thank you for your help!

Definitely a good idea.

Great thanks!