In my experience, there is no fixed timeline between a background check changing from "Not Applicable" to "We are processing" and receiving the Final Decision (FD). Even if an application is tagged as non-complex, the remaining security, criminality and other background verifications can take different amounts of time. One important thing to remember is that a change in the background check status does not necessarily mean that the final decision is just around the corner.
I would suggest checking your GCMS notes to see whether eligibility, criminality and security have been completed or are still in progress.
Hopefully, your application is approaching the final stage. Good luck, and please keep us updated!