Now with your latest details, a raw approach. As you are on a stock ROM, switching GPS might not work out-of-the-box. In case it doesn't work, take a look at the Secure Settings plugin, which should be able to help out.
I assume your raw concept is: 8am to 5pm is work time, and you want different settings during work hours and after leaving work, considering eventual late-work issues. So this should preferably turn out as a single profile: At work do... and After work switch to.... So here's what shoud basically work:
- Misc -> GPS: On (might need to be replaced by Secure Settings, see above)
Now we enter a second profile, and you probably do not even need GPS:
- State -> Tasker -> Profile Active: "Work" [x] Invert
- State -> Phone -> Cell Near: (Scan your work cells) [x] Invert
- Audio -> Silent Mode: Off
So you see you neither need GPS nor the 15min wait loop. At 8am the "Work" Profile gets active, and switches your phone to silent mode. As you do not really need GPS, you can define some dummy Exit Task here (e.g. again switching Silent Mode on), as otherwise Tasker would automatically revert to the "before" mode.
The second profile does not even check conditions before "Work" has completed, as Tasker remembers which Profiles are active. After that, it starts monitoring the surrounding mobile cells -- which are either known by the phone as needed for telephony. If none of the surrounding cells match any of the scanned cells, the attached task is executed and Silent Mode turned off.
But why so complicated? Much easier done like this:
- Cell Near (Scan your work place mobile cells)
Done. No matter what time you are at work, your phone will be silent. And no matter whether you leave work early or late, Silent Mode will be switched off.