Arduino Mega + sim900

[jazpiroz]

Dear, I am trying to connect to the internet using:
Arduino MEGA
SIM900, powered separately with a 9 volt source.
Bookseller: MarcoMartines / GSM-GPRS-GPS-Shield

I manage to send sms, make calls, etc., but I can not connect to the internet using the example:
GSM_GPRSLibrary_Client.ino

The sim900 raises ok, but at the time of making the connection it gives me status: ERROR.

I configure the apn of ancel.lte of uruguay.
It does not have a username or password.

Any suggestions ???
Of course, thank you very much to everyone!!
regards
Juan