From what I understand, you are using Standard GKE not Autopilot GKE.
Using node auto-provisioning GKE documentation provides much information about this feature.
Regarding your issue, you mention that your cluster didn't have node auto-provisioning and you have enabled it.
In Enabling node auto-provisioning part you have note:
If you disable then re-enable auto-provisioning on your cluster, existing node pools will not have auto-provisioning enabled. To re-enable auto-provisioning for these node pools, you need to mark individual node pools as auto-provisioned.
In short, if you just enabled auto-provisioning on cluster using:
gcloud container clusters update CLUSTER_NAME \
--enable-autoprovisioning \
... (other config)
It will work for new node-pools.
To enable node auto-provisioning for already existing node-pools, you need to specify it by name:
gcloud container node-pools update NODE_POOL_NAME \
--enable-autoprovisioning
If you didn't change anything, the first node-pool in the new cluster by default is called default-pool. So for example you should use
gcloud container node-pools update default-pool \
--enable-autoprovisioning
If this won't solve your issue, please provide more details about your cluster, what commands you execute in order to replicate this behavior.