Thank you for guiding me in here. I did no know about this log spot! 
The issue was that i in the first procedure (obviusly) was trying to remove a device wich where still in use. This it did not accept. And therefore always failed after this. When i sa wich one in the logs and added that again, it worked!
Manage to add the devices in the new Smarthings app
I needed to wait for about 5 min before I can add my phones but now it works .
I just modified my automatic scenes and my virtual presence sensors and looks good for now .
I will update you guys in about a week if it still works.
Question about the āSeconds elapsed to mark device offlineā what is the best practice? I setup 60 seconds but donāt know if this is the best setupā¦
@medxion, awesome! Glad things are working out for you so far . There really isnāt a ābest practiceā here. I my self, use 60 seconds. I know my cousin uses something like 5 seconds. It really just depends on how quickly you want your devices to be marked as being offline. If itās too short and you reboot your phone for example while you are home, it may trigger any away automations you may have setup. So it really just depends what works best for you.
I use the 180 seconds for now, works fine for me. Only thing that I needed to change was the Automatic disable alarm scene . I needed to add my manual alarm switch so if this one is status: On this scene doesnāt trigger when I am asleep and disables my alarm when my phone goes in sleep modus and disconnects its wifi haha.