JupyterHub user pod can't assume EKS node role

I installed JupyterHub with Helm on an EKS cluster, although the EKS service role can be correctly assumed by the hub pod (whose name starts with “hub-”), the user pods (starting with “jupyter-USERNAME”) seem can’t assume the role. Because of this, when a user uses boto3 in her notebook, she is asked for her IAM user credentials, which is not ideal.

All other pods in that namespace can assume the EKS role automatically except for the JupyterHub user pods. May I have your advice on this please? Thanks everyone for your time and consideration.

(I raised the same problem on StackOverflow as well. Thanks.)