Cannot delete network interface?

More information, i.e. what service would be helpful I guess. You can find the ENIs your account uses under the EC2 service page. Apparently a service was created that is using it, maybe a VPC endpoint, that you need to delete first?

Try this:

First go to the EC2 service dashboard, then select the "EC2 Global view" menu - There you'll have two menu options, Region Explorer and Global Search.

You'll be able to see what you've currently deployed in AWS and certainly spot your instance or service you're interested by.

Regards

I was able to connect with AWS support chat. Extremely patient and helpful. Ultimately, it was a database I had running in another region. Once I deleted that, I was able to delete VPC no problem. So problem resolved. Is there a screen of all running services that would be helpful in similar situations?