Laptop not going to sleep mode

Hi,

I got this dell inspiron 2 years ago. Just about 3 days ago, my laptop stopped going to sleep mode. My screen does turn off, but fans are running and power bottom still light up. The only thing I did different 3 days ago was restart laptop for adobe update.

All my power settings are correct, no errors found from troubleshooting and command prompt shows that there is no application stop my laptop from going to sleep. I also try to unplug both USB devices, as well as update my drivers.  

One thing I did notice is that the laptop does go to sleep in safe mode. But I don’t know where to find which service / application is the issue.

Does anyone know how to find it? Or I just need to do series of trials and errors? 

Thank you