Scheduler does not running 0x8004131F

I want to run the PHP script every 5 min, so i have created VBScript and this VBScript will kick the PHP Application, This VBScript will be configured in the Scheduler task in control panel. Scheduled job never ran getting following error code An instance of this task is already running. 0x8004131F .

Updated Note:

Finally today i have identified the scheduler problem. i have two users both users have same privileges (administrator). consider user1, user2.

When i schedule the SCRIPT under user1. Script will initiate automatically as per scheduled time.

But when i schedule the SCRIPT under user2. Script will no ran. as well i am getting mentioned error. " An instance of this task is already running. 0x8004131F ".

Still this issue not resolved for me.

you choose the option "Do not start a new instance, If the task is already running, then the following tule applies" in this task's settings.