Attempting MQTT connection...failed, rc=-2 try again in 5 seconds problem - mqtt

Question

A month ago, I created a code and uploaded it to the NodeMCU (ESP8266) in which the NodeMCU establishes connection with the aREST.io MQTT broker. It worked properly.
The code:
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <aREST.h>
WiFiClient espClient;
PubSubClient client(espClient);
aREST rest = aREST(client);
char* key = "the api key in aREST account";
const char* ssid = "SSID";
const char* password = "Pass";
#define trigger 5
#define echo 4
float distance;
void callback(char* topic, byte* payload, unsigned int length);
void setup(void)
{
Serial.begin(115200);
pinMode(trigger, OUTPUT);
pinMode(echo, INPUT);
rest.setKey(key);
client.setCallback(callback);
rest.variable("distance",&distance);
rest.set_name("esp8266");
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.println("WiFi connected");
}
void loop() {
rest.handle(client);
digitalWrite(trigger, HIGH);
delayMicroseconds(10);
digitalWrite(trigger, LOW);
int timin = pulseIn(echo,HIGH);
distance = (171.5*((timin)))*10E-5;
delay(60);
rest.publish(client, "distance", distance, 60000);
}
void callback(char* topic, byte* payload, unsigned int length) {
rest.handle_callback(client, topic, payload, length);
}
At the moment, the ESP8266 can't connect to the broker. It prints the following message after it connects to WiFi on the serial monitor:
"Attempting MQTT connection...failed, rc=-2 try again in 5 seconds"
I checked the API key about 5 times. it's the right one
I analyzed the network with wireshark and obtained the following:
As shown in the photo, the ESP8266 sends a CONNECT data packet to the aREST broker. The broker responds with the CONNACK packet. It's repeated every 5 seconds the content in the CONNECT packet:
the content of the CONNACK:

Answer 1

I believe the issue may be that the broker is down.
Your code looks like a modified version of the 'ESP8266_cloud.ino' code found in the ArduionIDE examples. I have an ESP8266 D1 and ran that example code with my own API plugin from aREST.io and get the same error message as you.
Running example code 'mqtt_esp8266.ino' I see interaction with my board to the broker, so I don't have reason to believe there's a general hardware or connectivity issue outside of the aREST broker.
Digging into aREST.h, the MQTT broker/server is 'mqtt.arest.io'
Checking on https://downforeveryoneorjustme.com/mqtt.arest.io, they say it's down.
Sorry that's not more helpful :/
I tried contacting the developer/the aREST Instagram page and have yet to hear back. Will keep you posted - please update your findings as well!