PnkBstrA disabled, how do I enable it?

First, do this steps: http://help.ea.com/en/article/battlefield-4-punkbuster-troubleshooting/ .

Also, try this additional steps, if the above does not work:

1. Open windows firewall

2. Click advanced settings( on the left) and then inbound (also left)

3. Find PnkbstrA.exe and PnkbstrB.exe (if you have two of both, its fine)
4. Right click on each of them>properties>programs and services
5. Make sure that "all programs that meet the specifications" is checked
6. Then go to the "Advanced" tab and check all 3 boxes. Domain, Private and Public.
7. REMEMBER TO DO THIS FOR ALL PnkBstr Files. Then save and quit.
8. Go to C:\Program Files (x86)\Origin Games\Battlefield 4 and delete "Pb" folder.
9. Go to these 2 links:
http://websec.evenbalance.com/downloader/download.php?file=1
http://www.evenbalance.com/downloads/pbsvc/pbsvc.exe
10. Download and install both
11. Run Pbsetup.exe (the first link)
12. Add a game (eg. bf4)
13. Check for updates.

Also, try to disable your firewall if it does not work.

You might also want to look at my Punkbuster guide:

http://answers.ea.com/t5/Battlefield-4/READ-FIRSTS-Common-issues-Fixes-amp-Guides/m-p/4362361#M175918