AccessDenied when calling the AssumeRole operation

python enablesecurityhub.py --master_account MASTERACCOUNTID --assume_role ManageSecurityHub --enabled_regions ap-south-1 enable.csv
Enabling members in these regions: ['ap-south-1']
Assumed session for MASTERACCOUNT ID.
Error Processing Account MEMBERACCOUNTID
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Failed Accounts
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XXXXXXXXX:
ClientError(u'An error occurred (AccessDenied) when calling the AssumeRole operation: User: arn:aws:sts::MASTERACCOUNTID:assumed-role/ManageSecurityHubInstanceRole/i-0a8a33c4f573xxxxx is not authorized to perform: sts:AssumeRole on resource: arn:aws:iam::MEMBERACCOUNTID:role/ManageSecurityHub',)
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Option 1 selected. [EC2 instance with enablesecurityhub]

Could see the same IAM roles in master account and member account. Ran CFT to create the roles and instance profile,policy. Not sure what am i missing here. Any assistance here please.