Look at the earlier post above "My Apps" is missing from Marketplace, SmartApps?! - #16 by vlad it seems you are needing to login using a different URL?
- Go to https://graph.api.smartthings.com
- Login and then click on My Locations, then click on your hub name.
- login again.
Thanks for all the great suggestions in this thread… however, I STILL could not get “My Apps” to show up.
Finally I realized that while logged in to the specific na02 server (the graph-na02-useast1.api.smartthings.com url), after logging out if I then paste the URL https://graph.api.smartthings.com/ into my browser I’m still logged in!
Previously, I’d realized that when logging in at the graph.api.smartthings.com url, and then clicking on my defined location, I had to login a second time. But I never realized that I’d have to logout TWICE, once from each of these locations.
After doing that, I did see “My Apps” show up… not in Marketplace, but it DID show up under Automations in the SmartApps tab.
Phweeeeew! 
OK I’m brand new to this but I had the same problem everyone else is having. I was trying to get the tonesto NST-Manager app to install. The first problem was I was using the wrong IDE link as someone pointed out above. HOWEVER after going to the https://graph-na02-useast1.api.smartthings.com and redoing everything as far as Github repo authorizing, publishing for me (make sure and do that under the “My SmartApps” AND the “My Device Handlers” links) logging out of the app, and resetting my Version 2 hub I still could not get the My Apps link to show up in the SmartThings iOS app. So here is how I stumbled across the answer:
Log out of the SmartApps website at “na02” Then try and log in at https://graph-na04-useast2.api.smartthings.com . Notice in the link instead of “na02” its “na04”. Dumb luck redirected me to that link. I had to redo EVERYTHING for a third time but the My Apps link finally showed up.
After spending hours trying to get the MyApps to show up, your post did the trick! Thank you for sharing!
Glad I could help!
Na02 did it for me too.
This is totally insane, but there are multiple url’s to go to in order to get the right information and do things. The trick to finding the right one- try all of these (may be more?)
https://graph-na04-useast2.api.smartthings.com/
https://graph-na02-useast2.api.smartthings.com/
https://graph.api.smartthings.com/ide/apps
Click on the devices tab. If you see your devices, that’s the right url.
I too had this problem and searched all over the place to figure out why I could not see the app in “My Apps”. The Nst Manager 5.0 installation docs offer up this link as a solution:
Use this link instead: https://consigliere-regional.api.smartthings.com
It should take you to your correct shard so that you don’t have to guess which one to start installing your apps on.
As a note the link has been shortened again to just https://account.smartthings.com
ok that worked for me but i am having trouble with the smart app i am trying to use now so doi need to go and delete the handlers and smart apps i added on the URL’s that did not have my devices listed? could that be causing a conflict?
For me, it was not about from URL I add new app (CoRe),
it was about making sure after i login, I got to “My Locations” and select the location and then add new application.