I had the same problem.
I use my dlink products connected to an Engenius router.
I tried to connect the new bought DCH S150 sensor to my DlinkHome app.
After trying several times I installed a D-link router DIR 605N , connected my smartphone and the sensor and within 3 seconds the sensor was connected to my DlinkHome app and everything worked fine.
Because my home network uses the Engenius router, I reconnected all my stuff back to the Engenius router and it keeps working.
So, Dlink says you can use it with all routers with WPS function but it does NOT.
Hope this helps solving your problem.
btw the same problem occurs with the DSP-W215 Smart Plug