Using Pushover Notification with Arduino

Hi, I have an arduino wired up to a pager and when the pager is activated, the arduino uses the code below to send a Notification to my smartphone telling me the pager has been activated, All works great.

Now I want to set up a group of people that will receive the same Notification when the pager is activated, This can be done my having a group userkey in place of my own userkey, But I get the following error :

{"errors":["messages to users other than the creator of this application (Pager) must be sent over SSL to https://api.pushover.net/"],"status":0,"request":"c0cf5a77ef6bt705f727352d08599a99"}

So it's got something to do with https and the HTTP in the code but I am unable to figure it out,
Can anyone help me with this or point me in the right direction

/*

  Pushover sketch by M.J. Meijer 2014

  Send pushover.net messages from the arduino

*/

#include <SPI.h>
#include <Ethernet.h>

byte mac[] = {0xDE,0xAC,0xBF,0xEF,0xFE,0xAA};

// Pushover settings
char pushoversite[] = "api.pushover.net";
char apitoken[] = "my api token here";
char userkey [] = "my uesrkey here";//My user key
int length;

EthernetClient client;
int analogPin = 3;   // analog input pin
int testButton = 3;
int testLed = 13;
int state =0;
void setup() 
{
pinMode(3,INPUT); 
digitalWrite(3, HIGH);
 
 Serial.begin(9600);
 Serial.print(F("Starting ethernet..."));
 if(!Ethernet.begin(mac)) Serial.println("failed");
 else Serial.println(Ethernet.localIP());

 delay(5000);
 Serial.println("Ready");
 analogReference(INTERNAL);    // select internal 1.1 volt reference

}

void loop()

{
 if ( digitalRead(3) == HIGH  ) { // Button not pushed
       digitalWrite(13, LOW ) ;       // Turn off the LED
} else {                                          // Button is pushed
       digitalWrite(13,HIGH);
       pushover("Test ");// Turn on the LED
}


 int aval = analogRead(analogPin); // sample analog input
 //Serial.println(aval);
 if (aval == 1023) {
 //pushover("OMG, Yes it works!!!");
 
 pushover("CALL");  
 delay(8000); 
 }
}

byte pushover(char *pushovermessage)
{
 String message = pushovermessage;

 length = 81 + message.length();

 if(client.connect(pushoversite,80))
 {
   client.println("POST /1/messages.json HTTP/1.1");
   client.println("Host: api.pushover.net");
   client.println("Connection: close\r\nContent-Type: application/x-www-form-urlencoded");
   client.print("Content-Length: ");
   client.print(length);
   client.println("\r\n");;
   client.print("token=");
   client.print(apitoken);
   client.print("&user=");
   client.print(userkey);
   client.print("&message=");
   client.print(message);
   while(client.connected())  
   {
     while(client.available())
     {
       char ch = client.read();
       Serial.write(ch);
     }
   }
   client.stop();
 }  
}

Can anyone help me with this or point me in the right direction

No. The Arduino can't do SSL.