What is your status when u check online? If it says In Process ,click on it u will see details, and if u have Medical results have been received (from 02 months after u did medical exam) then no worry , they previewing your background.
Thats mean u gave them wrong answear, double check all your answear, make sure are the same u gave them in your application, did u get progress bar after March 6 email?
After creat GCkey , there an link said about link your application, u have to answear somequestion to verify your application, make sure u choose right option and family questions.
Here my timeline:
-Received my app Jul 2018
-Process in Dec 2018
-Medical exam Dec 2018
-Medical has received and passed Feb 2019 after called CIC,
-Now they review my background