With a Samsung account, you need one of your locations to be the “default location”. If you try to delete a location that is the default, you will receive a 500 error. Most of the time, you can switch which location is your default though.
This is under the location settings when you click “Edit” for a location in the IDE:
Ok…
So, I got kicked out of the classic app.
It won’t let me sign in with my ST credentials, it just pushes me to my samsung account.
I have NOT completed migration.
The system is alive and armed (I figured that out when I opened the door), sirens are on, but I have nothing on the app.
It’s literally blank and ready to setup.
How do I get back to my ST account settings?
I would call support, 800-SAMSUNG.
Screwed me too. Exactly the same. Just emailed support to see if they can sort out this seamless migration. 
Making those of us with non-Samsung android phones install the Samsung browser diminished Samsung’s reputation from my perspective. Also, installed a new location “Home” which cannot be removed… really?
Yeah, when it adds the extra HOME, it also sets it as DEFAULT in the new app. What you need to do in the new app is set your real HOME as the default, then you can delete the extra HOME … that’s what worked for me.
There are many threads about this on the forum and it seems to be the solution to issues many folks are seeing. A search will turn up a number of other problems with the new app—apparently a work in progress…
This has been going on awhile and I have yet to receive any notification to switch over, which to be honest, I have been happy about. Everything has been working, so if it ain’t broke…
I am, however, about to purchase a new home and will have to set everything up again, so I wondered if I can go ahead and switch when I move to the new house or should I just keep waiting?
Where, pray tell, is this mysterious location to change the DEFAULT setting? I have looked in the app and the portal to no avail. I click the red “Remove Location” in the app and it fails. Many thanks in advance kind sir.
Go to the IDE and you should select your actual location and find a button/drop-down for Default Location.
Had my notification a coupled of days ago. I never had a Samsung account before and I am an iOS user with a single location and hub. First step was to delete the contacts. Sad to have to do, but since it wasn’t supported feature anyway I am not too stressed by it. The migration went 100% smoothly. Have not even tried to down load the new APP and will not be doing so until I know I will be better off.
to delete a Home Location that has nothing in it:
If that does not work, please contact ST support at https://support.smartthings.com 
Awesome. I was logging into https://graph.api.smarthings.com - I guess I have missed a few things Thanks Gentlemen
We really need a pinned topic for troubleshooting migration issues with this pasted in it. @Brad_ST thoughts?
It actually needs to be part of the notification that shows up on the app. Some people do not even know about the community.
Understatement of the century award 
!
So “some people” = hundreds of thousands of people.
Hopefully those people are reaching out to support directly
Yup. Same here. Still unable to migrate (even if I wanted to) since it just goes to an error page that requires you to install Samsung’s shitty browser or Chrome.
Fvck this. Even Edge uses Chrome’s rendering engine on Android, so there is no excuse for this not working, expecpt for Samsung trying to push their shitty browser.
Actually, it’s not. I did it all without using chrome or the samsung browser.
Out if interest, do you know how many hubs that maps to?
If its been anywhere near marketing, that figure will include anyone who has ever downloaded either Smartthings app or has been added as an additional user to a hub.
