Hey Stan,
There has been a fair amount of discussion around the new motion sensor as it is actually only new to the US market and was released in other markets earlier. You can read through the convo here: Ikea motion sensor - #74 by BroderickCarlin
To answer your question though, yes, IKEA products work with SmartThings but there are some limitations if you are using legacy SmartThings products (like the V1 hub)
Yeah, the DTH only has a single fingerprint because IKEA gave both the old and the new motion sensor the same model name 
Therefore they can both share the same fingerprint
To get to the problem though, if you are still having issues getting the sensor to join feel free to shoot me a PM with the email address associated with your SmartThings account and I can look to see if there is any issues from our side as to why the sensor is not joining