Elastic Beanstalk could not find any platforms

Your IAM account does not have permission to access Elastic Beanstalk. Contact your IAM admin and have the admin grant your account full Elastic Beanstalk permissions.

rm ~/.aws

This fixed the issue for me (updating ~/.aws/config or ~/.aws/credentials in here didn't help)

I had this issue as well. There is a file in /Users/USER_NAME/.aws/ called config.

It looks like below -

[profile eb-cli]
aws_access_key_id = <ACCESS_KEY>
aws_secret_access_key = <SECRET_ACCESS_KEY>

Update this file with your updated aws_access_key_id & aws_secret_access_key

Credit: How to change the AWS account using the Elastic Beanstalk CLI

Problem is, as @helloV said, your user does not have access. Now this was a complete surprise to me because I was using the root (which I really shouldn't) and I ASSUMED it would just have access.

So solution is that you HAVE TO ATTACH a policy as shown in the screenshot below since even the root IAM account does not have this policy.