I had SIM900 Shield and i use a 12V-2A power adapter , the Power Led is light on when i connect the power,
but when i press the power key it was lighting the STA's LED but now nothing is happening to that led....i
checked all the voltages on the I/O to the LDO,Power Pins of the SIM900 & checked the LEDs if they are
fault...every thing is OK....but the Module is still not responding to the Power Key Press...
This is How it Should Look Like (STA's LED is ON...Blue Led)
This is What I get even if i press the Power button
so what could be the problem !!?
while i was searching for a solution i found some one who made a video about the same Issue , if you didn't
understand my explaination of the problem here's his Video
https://www.youtube.com/watch?v=ejytfD8y-uc