AWS Cognito Identity Pool stopped working when idenity pool auth role is changed

Question

We have configured one user pool in AWS Cognito. There are no User Pool Group Roles configured. We had configured authenticated access with new IAM role under User Access section in Identity Pool which is assigned to this User Pool. This setup and user access as per Identity Pool Auth Role were working as expected. This IAM Role was assigning access to specific S3 bucket and few permissions for IOT. However, we tried changing IAM Role under Authenticated Access to deny the previous permissions related to S3 Bucket Access to users and changed the IAM role back to the original IAM role. Now after the user logs in, Cognito identity pool stopped working and started throwing 403 Forbidden Error. It looks like changing back to the original IAM Role is not working anymore. All these operations are done via AWS Console. We can't recreate User Pool. How can we debug and solve this issue?