How can I recover the ESPN app on Apple TV

The firmware is the version of software currently running on Apple TV

If you really had the 1st Gen, big aluminum box, then it never had any 3rd party content apart from YouTube (which google dropped when it updated its API).

If it's a small black box then that's the 2nd Gen. That had access to preset 3rd party content sent via server, but no apps. If it was something that you had access to before make sure it hasn't been hidden by going into settings - general - main menu. Providers have also focused their efforts in the current Apple TV's (4th Gen and 4K) which do run apps so you may need to contact them to see if they still support the older model.

You can use airplay from your iPhone/iPad, but if you want native apps that's always required a 4th gen or 4K model. Support has also dropped from some of those older server based versions as providers focus on those apps.

The 2nd gen is also considered obsolete, with that last update being around 4 years ago and no further support for software or hardware.

Apparently the ESPN support has stopped for these older devices, as another user found out after a call.

Re: ESPN no longer on my Apple TV Gen 3

What Apple TV model? What firmware is it running?

That is a 2nd Gen, which I had referred to in my previous response.