GPRS GSM SIM900 communication

Hello friends,

I have a GSM shield model that I'm trying to connect to my Arduino UNO board. I'm using a library and a tutorial that I found here but I'm having a lot of trouble trying to configure the ports for communication. Following the video in the tutorial I decided to do soldering over the pins to make the communication and stack the shield over my Uno board.

My shield lights up when I connect my Uno through USB but only lits the net and status led when I press the power button. The status led stays on for some seconds while the net one blinks in a rate of 800ms. I did set up the ports on the library for pins 2 and 3 also checking that in the board there's pins with a movable cap joining two pairs of them by the side of the pins 2,3 and 4 over my Uno board.

My Serial Monitor takes some time to start printing something, but it's an error:

11:23:34.484 -> Trying to force the baud-rate to 9600

11:23:34.578 ->

11:23:34.578 -> 1200

11:23:45.088 -> 2400

11:23:55.653 -> 4800

11:24:06.225 -> 9600

11:24:16.741 -> 19200

11:24:27.257 -> 38400

11:24:37.776 -> 57600

11:24:48.293 -> 115200

11:24:57.825 -> ERROR: SIM900 doesn't answer. Check power and serial pins in GSM.cpp

11:24:57.918 ->

11:24:57.918 -> status=IDLE

How can I handle this? Does anyone know what may be happening? Is it related to my power feeding or the ports that are wrong?