I'm having the same problem. I have found a way to get to the app's page on iTunes Connect, however, even though it's not showing up anywhere (not even in the drop-down list). What I found was that, although the app is not showing up in iTunes Connect in any web browser, it *is* showing up in the iTunes Connect iOS app. So, to get to the page:
1. In the "Connect" app on iOS, go to the app page.
2. Note the Apple ID of the app.
3. In Safari on your Mac, go to iTunesConnect and open the page for an existing app.
4. Replace the app ID at the end of the URL with the app ID you noted down from the iOS app.
This lets me get to the app page and edit it even though it's not listed. I'm currently trying to upload a build to see if that makes the app visible. A very silly bug, though!
EDIT: I've now uploaded a build, selected it in the app's page in iTunes Connect, and the app is now showing in the list of apps at last. Hopefully this will help fix it for someone else too.