Error:AWS Control Tower failed to set up your landing zone completely: AWS Control Tower setup failed. Be sure your account is subscribed to the AWS EC2 service, then try again. If this error persists

It appears that you're encountering an issue while setting up AWS Control Tower, despite having already launched an EC2 instance. This suggests that the problem may not be directly related to EC2 subscription or billing details.

Given that Control Tower is failing to set up your landing zone completely, there could be a few potential causes:

1. Account activation: Sometimes, newly created AWS accounts may not be fully activated for all services immediately. Even though you've successfully launched an EC2 instance, there might be a delay in activating all the necessary services for Control Tower.

2. Permissions: Ensure that you have the necessary permissions to set up Control Tower. You should be using an account with administrative privileges.

3. Service quotas: Check if you have any service quota limits that might be preventing Control Tower from setting up properly.

4. Region-specific issues: Make sure you're setting up Control Tower in a supported region and that there are no region-specific service outages.

5. Existing resources: If you've already attempted to set up Control Tower before, there might be lingering resources causing conflicts.

To resolve this issue, you can try the following steps:

1. Wait for 24-48 hours after account creation to ensure all services are fully activated.

2. Double-check that you're using an account with full administrative access.

3. Review your service quotas and request increases if necessary.

4. Try setting up Control Tower in a different supported region.

5. If you've attempted setup before, you may need to manually clean up any existing Control Tower resources or configurations.

If the issue persists after trying these steps, it's recommended to contact AWS Support for further assistance. They can provide more specific guidance based on your account's status and configuration.
Sources
Tried to enable Control Tower with defaults but it failed to activate the accounts and couldn't finish the landing zone process | AWS re:Post
Cancel instead of Retry on Control Tower Failure to setup Landing Zone | AWS re:Post