Library comply failed

[thefuriousowl]

I tried to verify example code in Arduino IDE Version 2.1.0 as per following:

#include <AIS_NB_BC95.h>


String serverIP = "my.ip.add.ress"; // Your Server IP
String serverPort = "myport"; // Your Server Port

String udpData = "HelloWorld";

AIS_NB_BC95 AISnb;

const long interval = 20000;  //millisecond
unsigned long previousMillis = 0;

long cnt = 0;
void setup()
{ 
  AISnb.debug = true;
  
  Serial.begin(9600);
 
  AISnb.setupDevice(serverPort);

  String ip1 = AISnb.getDeviceIP();  
  delay(1000);
  
  pingRESP pingR = AISnb.pingIP(serverIP);
  previousMillis = millis();

}
void loop()
{ 
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval)
    {
      cnt++;     
           
      // Send data in String 
      UDPSend udp = AISnb.sendUDPmsgStr(serverIP, serverPort, udpData+String(cnt));
   
      //Send data in HexString     
      //udpDataHEX = AISnb.str2HexStr(udpData);
      //UDPSend udp = AISnb.sendUDPmsg(serverIP, serverPort, udpDataHEX);
      previousMillis = currentMillis;
  
    }
  UDPReceive resp = AISnb.waitResponse();
     
}

But always got this error from Arduino IDE

AIS_NB_BC95.h:84:3: error: 'signal' does not name a type
   signal getSignal();
   ^~~~~~

exit status 1

Compilation error: exit status 1

Even I try to change library version to 1.0.0 or 1.0.5. This error still occurred.