Cannot activate the AWS-generated tags cost allocation tags.

It's strange, I haven't encountered this before. These tags are auto-applied to resources by AWS with the format aws:. They will only appear here if resources are tagged with them. Does this account have provisioned resources? There is also this special aws:createdBy that doesn't show up in the console, but aws internally adds to resources, albeit available only in specific regions: https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/aws-tags.html

Hello,

Only a management account can activate AWS-generated cost allocation tags. This means that a non-management account will not be able to see the AWS-generated cost allocation tags in the Billing and Cost Management console.

https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/aws-tags.html#aws-tag-restrictions