Problem acquiring data on esp32 for geiger counter

I bought the same boards used in this video on Youtube (the componts are THIS geiger counter (that I am pretty sure its working, the tiks on the speacker are coerent) and THIS esp (I don't know if is here the problem or in the code), I loaded the arduino code into the esp32 board, but the display remains stuck on "Measuring". It connects correctly to the ThingSpeak channel, but always linearly increasing measurements. The number grows continuously (view the attached image). I tried to insert some currentMillis and previousMillis println. Both variables are always 0 in the serial monitor. So I tried adding currentMillis = millis (); at the beginning of the loop (), at this point the display has finally shown "radioactivity" with the usual increasing numbers. Even if the card is disconnected from the geiger counter, the data are the same and always increasing. How can I solve it?

#define PRINT_DEBUG_MESSAGES

#include <WiFi.h>
#include <WiFiClientSecure.h>
#include <IFTTTMaker.h>
#include <ThingSpeak.h>
#include <SSD1306.h>
//#include <credentials.h> // or define mySSID and myPASSWORD and THINGSPEAK_API_KEY

#define LOG_PERIOD 20000 //Logging period in milliseconds
#define MINUTE_PERIOD 60000
#define WIFI_TIMEOUT_DEF 30
#define PERIODE_THINKSPEAK 20000

#ifndef CREDENTIALS
// WLAN
#define mySSID ""
#define myPASSWORD ""

//IFTT
#define IFTTT_KEY "......."

// Thingspeak
#define SECRET_CH_ID 000000      // replace 0000000 with your channel number
#define SECRET_WRITE_APIKEY "XYZ"   // replace XYZ with your channel write API Key

#endif

// IFTTT
#define EVENT_NAME "Radioactivity" // Name of your event name, set when you are creating the applet


IPAddress ip;

WiFiClient client;

WiFiClientSecure secure_client;
IFTTTMaker ifttt(IFTTT_KEY, secure_client);
SSD1306  display(0x3c, 5, 4);

volatile unsigned long counts = 0;                       // Tube events
unsigned long cpm = 0;                                   // CPM
unsigned long previousMillis;                            // Time measurement
const int inputPin = 7;
unsigned int thirds = 0;
unsigned long minutes = 1;
unsigned long start = 0;
unsigned long entryThingspeak;
unsigned long currentMillis = millis();

unsigned long myChannelNumber = SECRET_CH_ID;
const char * myWriteAPIKey = SECRET_WRITE_APIKEY;

#define LOG_PERIOD 20000 //Logging period in milliseconds
#define MINUTE_PERIOD 60000

void ISR_impulse() { // Captures count of events from Geiger counter board
  counts++;
}

void displayInit() {
  display.init();
  display.flipScreenVertically();
  display.setFont(ArialMT_Plain_24);
}

void displayInt(int dispInt, int x, int y) {
  display.setColor(WHITE);
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(x, y, String(dispInt));
  display.setFont(ArialMT_Plain_24);
  display.display();
}

void displayString(String dispString, int x, int y) {
  display.setColor(WHITE);
  display.setTextAlignment(TEXT_ALIGN_CENTER);
  display.drawString(x, y, dispString);
  display.setFont(ArialMT_Plain_24);
  display.display();
}


/****reset***/
void software_Reset() // Restarts program from beginning but does not reset the peripherals and registers
{
  Serial.print("resetting");
  esp_restart();
}


void IFTTT(String event, int postValue) {
  if (ifttt.triggerEvent(EVENT_NAME, String(postValue))) {
    Serial.println("Successfully sent to IFTTT");
  } else
  {
    Serial.println("IFTTT failed!");
  }
}

void postThingspeak( int value) {
  // Write to ThingSpeak. There are up to 8 fields in a channel, allowing you to store up to 8 different
  // pieces of information in a channel.  Here, we write to field 1.
  int x = ThingSpeak.writeField(myChannelNumber, 1, value, myWriteAPIKey);
  if (x == 200) {
    Serial.println("Channel update successful.");
  }
  else {
    Serial.println("Problem updating channel. HTTP error code " + String(x));
  }
}

void setup() {
  Serial.begin(115200);
  displayInit();
  ThingSpeak.begin(client);  // Initialize ThingSpeak
  displayString("Welcome", 64, 15);
  Serial.println("Connecting to Wi-Fi");

  WiFi.begin(mySSID, myPASSWORD);

  int wifi_loops = 0;
  int wifi_timeout = WIFI_TIMEOUT_DEF;
  while (WiFi.status() != WL_CONNECTED) {
    wifi_loops++;
    Serial.print(".");
    delay(500);
    if (wifi_loops > wifi_timeout)
    {
      software_Reset();
    }
  }
  Serial.println();
  Serial.println("Wi-Fi Connected");
  display.clear();
  displayString("Measuring", 64, 15);
  pinMode(inputPin, INPUT);                                                // Set pin for capturing Tube events
  interrupts();                                                            // Enable interrupts
  attachInterrupt(digitalPinToInterrupt(inputPin), ISR_impulse, FALLING); // Define interrupt on falling edge
  unsigned long clock1 = millis();
  start = clock1;
}

void loop() {

  if (WiFi.status() != WL_CONNECTED)
  {
    software_Reset();
  }

  if (currentMillis - previousMillis > LOG_PERIOD) {

    previousMillis = currentMillis;

    cpm = counts * MINUTE_PERIOD / LOG_PERIOD;
    //cpm=105;
    counts = 0;
    display.clear();
    displayString("Radioactivity", 64, 0);
    displayInt(cpm, 64, 30);
    if (cpm > 100 ) IFTTT( EVENT_NAME, cpm);
  }
  // Serial.print("minutes: ");
  // Serial.println(String(minutes));

  //cpm = counts * MINUTE_PERIOD / LOG_PERIOD; this is just counts times 3 so:

  cpm = counts / minutes;


  if (millis() - entryThingspeak > PERIODE_THINKSPEAK) {
    Serial.print("Total clicks since start: ");
    Serial.println(String(counts));
    Serial.print("Rolling CPM: ");
    Serial.println(String(cpm));
    postThingspeak(cpm);
    entryThingspeak = millis();
  }

  //    if ( thirds > 2) {
  //      counts = 0;
  //      thirds = 0;
  //    }
}

This is based on this work on GITHUB