I have moved to the new app but do not see how to arm & disarm my setup. On the old app, the home page had armed, disarmed, and away can not see it on the new app.
Mike
What region are you in? STHM is region locked and not available in many countries. If you do not see it on your dashboard after the migration, or can’t see it in add smartapp from the + (plus) menu in the upper left of the screen, or do not see it listed in menu > SmartApps- then most likely it is not available in your region 
Or if you are in a country where it is available, perhaps the migration assigned your account to a different country.
Contact ST support and open a support ticket
I live in north-central Florida. Here is a picture of my home page, my + is on the right side I see Smart App but nothing about the dashboard. If I am not able to set away or vacation ho9w do I get my lights to work?
Mike
Ahh, that is a different story…
Go to the menu, select Smartapps, click on More options (3 dots in the upper right of the screen) and choose delete, select SmartThings Home Monitor and delete it. Then click on the + (plus) in the upper right of the screen and choose smartapp and choose SmartThings Home Monitor to add that app back. Then check to your dashboard to see if it loads correctly. Then reconfigure your STHM settings.
Did not work SmartThings Home Monitor does not delete
Does your hub show in menu > devices and if yes… is it assigned to a room?
But is your Home hub listed in that list?
My hub is named Home so based on the 2 pictures I guess it is listed, Guess I am just a dumb old man.
click on menu and open Devices…look for it there. it should appear like any other device. If it does not show up… contact ST support
it needs to be assigned to a room. click on the 3 dots in the upper right of the screen, choose edit and assign the hub to a room.
what is that Home right above it that shows offline?
after you assign the hub to a room, you may want to restart the hub in IDE to see if it resolves those offline devices