Think of it this way, there are multiple shards or servers for SmartThings. Each server is set up with the same parts - a place to load SmartApps, Device Handlers, etc. But, each of us is only located on one shard. If you happen to be logged in to the wrong server it is possible to load SmartApps and Device Handlers but they won’t then show up in the app on your phone (which can only be pointing to the right shard for you).
When I had you click on Location then Maya, that forces your IDE to point to the right shard for you (ie, the same one your phone app is connected to). Once on the right shard in the IDE you can click on My SmartApps (the fourth item along the top) and install the apps you want. They will then show up on the app on your phone.
All that said, I am a little confused myself if you are seeing that screen with webCoRE loaded after clicking through location/Maya.