On the background check (BC) you start as "Not Applicable" so NA (used to be Not Needed so NN), usually when your medicals finally change to passed your BC will change to something like "We are preparing to process your BC", this used to be the status "Not Started" so NS. The other status you'll also see (albeit closer to the end of your process) is "We are processing your BC" this is known as IP, because in the pass it used to be "In Progress". So you're probably at NA, it will typically change to the "We are preparing..." when your medicals change and a few days later (maybe weeks these days) it will eventually return to NA.
BG Not Started/ Not Applicable ------> In Progress
BG In progress ------> No needed/Not Applicable
BG Not Needed ------> In progress. This will stay like this untill you get your PPR.
You may also like to search the forum for GCMS notes and understand about various changes in application status...
