How to get rid of CMS ERROR 2051 in quectel m66

Question

I am working in a gsm shield and sometimes(after 1 week) I get CMS ERROR 2051 while sending SMS. How can i solve this. In data sheet it says ILLEGAL MS

What is MS and how is it illegal?

Here is my setup before trying to send sms. I am using quectel m66, raspberry pi and python. Do I need to do some extra initialization?

serialPrintf(fd,"AT+IFC=1,1\n");                    // Set TE-TA Control Character Framing
delay(300);
serialPrintf(fd,"AT+CMGF=1\n");                     //Select sms format
delay(300);
serialPrintf(fd, "AT+CPMS=\"SM\",\"SM\",\"SM\"\n");
delay(300);
serialPrintf(fd,"AT+CLIP=1\n");                     //Calling Line Identification Presantation
delay(300);
serialPrintf(fd,"ATE0\n");//?
delay(5000);
serialPrintf(fd,"AT+COLP=1\n");                     // Connected Line Identification Presentation
delay(300);
serialPrintf(fd,"AT+CSCS=\"IRA\"\n");               //Select TE Character Set
delay(300);
serialPrintf(fd,"AT+QCCID\n");                      //Show ICCID
delay(300);