@glenmm - I just went through this with my 2 ST anything enabled devices and I had similar issue so I can share what worked for me:
The first one I removed both the parent and child devices. I re-added the parent and filled in the settings in the IDE. I too noticed that the parent device showed up as a Presence sensor but ultimately this didn’t impact anything and I don’t use the parent. My child device was successfully created but I was getting a similar “network or server error”. I tried the refresh while looking at the live logging and saw that there was a java exception in the DTH. It turns out that the default settings in the child device were somehow causing an exception (almost like they were blank). Once I filled values for each setting (different than the default), the exception went away and I was able to successfully use the device in the new app.
The second one I just deleted the children based on the earlier recommendations. I rebooted my device and waited but no children were created. I left it overnight and tried a refresh with no success. I opened the parent device in new smartthings app and tried to fill in the settings, but it wouldn’t let me save a value in the timeout field. I then opened the parent device in the IDE and checked the settings. I noticed that the timeout value was blank so I filled in the suggested 900 value and saved the settings. I then went to the live logging to see if I had a similar issue as the first device and saw all the children getting created. Everything now looks to be ok.
Long story short - I’d start by making sure all setting are filled in on the parent in the IDE and then go into any children and make sure they have values filled in for their settings.
@ogiewon - I know this platform is not your priority anymore but thank you soo much for making the updates so that ST_anything works in the new app