Arduino Pro Mini 8Mh with TPL5110 (mini-lora)

I built a device as described in https://github.com/hallard/Mini-LoRa. The device runs as long, as I do not use the TPL5110 part of it. When I try to implement the sleep mode using TPL5110, nothing changes (see code below). My question is: How does one implement the sleep mode using TPL5100 right, so that the Arduino Pro Mini is woken up regularly by tpl5110? Any suggestion is welcome! (I am trying now for months without success).

#include <RH_RF95.h>
#include <RHDatagram.h>
#include <CayenneLPP.h>
#include <EEPROM.h>
#include <BME280I2C.h>
#include <Wire.h>
#include <Lora_Config.h>

///////////////////////////////////////////////////////////////////
// START CONFIGURATION
///////////////////////////////////////////////////////////////////
#define RF95_CLIENT_DEBUG
#define SERIAL_BAUD 115200
///////////////////////////////////////////////////////////////////
// END CONFIGURATION
///////////////////////////////////////////////////////////////////

#define EEADDR 128
#define DONE_PIN A1

Lora_Config data;

BME280I2C bme;    // Default : forced mode, standby time = 1000 ms, Oversampling = pressure ×1, temperature ×1, humidity ×1, filter off,
CayenneLPP lpp(51);
RH_RF95 rf95;
RHDatagram manager(rf95);

volatile float h; // Relative Humidity
volatile float t; // Temperature
volatile float p; // Presure
volatile float v; // Voltage
const int pwr_down_loops = 150;

float readVcc()
{
  long result;
  // Read 1.1V reference against AVcc
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
  delay(2); // Wait for Vref to settle
  ADCSRA |= _BV(ADSC); // Convert
  while (bit_is_set(ADCSRA, ADSC));
  result = ADCL;
  result |= ADCH << 8;
  result = 1126400L / result; // Back-calculate AVcc in mV
  return float(result) / 1000;
}

void setup() 
{
  Wire.begin();
  pinMode(DONE_PIN, OUTPUT);

#ifdef RF95_CLIENT_DEBUG
  Serial.begin(SERIAL_BAUD);
#endif

  EEPROM.get(EEADDR, data);
#ifdef RF95_CLIENT_DEBUG
  Serial.println("=== Read EEPROM ===");
  Serial.print("node_addr: ");
  Serial.println(data.node_addr, DEC);
  Serial.print("gateway_addr: ");
  Serial.println(data.gateway_addr, DEC);
  Serial.print("lora_frequency: ");
  Serial.println(data.frequency, DEC);

  Serial.print("Initializing LORA module ");
#endif
  manager.setThisAddress(data.node_addr);
  if (manager.init())
  {
#ifdef RF95_CLIENT_DEBUG
    Serial.println("OK");
#endif
    rf95.setFrequency(data.frequency);
  }
  else
  {
#ifdef RF95_CLIENT_DEBUG
    Serial.print("Failed");
#endif
    while(1);
  }
#ifdef RF95_CLIENT_DEBUG
  Serial.print("Initializing BME280 sensor ");
#endif
  if (bme.begin())
  {
#ifdef RF95_CLIENT_DEBUG
    Serial.println("OK");
#endif
  }
  else
  {
#ifdef RF95_CLIENT_DEBUG
    Serial.println("failed");
#endif
  }
  delay(1000);
}

void loop()
{
#ifdef RF95_CLIENT_DEBUG
  Serial.print("Reading current Voltage: ");
#endif
  v = readVcc();
  
#ifdef RF95_CLIENT_DEBUG
  Serial.print("Reading sensor data: ");
#endif
   float t(NAN), h(NAN), p(NAN);

   BME280::TempUnit tempUnit(BME280::TempUnit_Celsius);
   BME280::PresUnit presUnit(BME280::PresUnit_Pa);
   bme.read(p, t, h, tempUnit, presUnit);
#ifdef RF95_CLIENT_DEBUG
  Serial.print("\n\tTemperature: ");
  Serial.print(t);
  Serial.println("C\n");
  Serial.print("\tRelative Humidity: ");
  Serial.print(h);
  Serial.println("%\n");
  Serial.print("\tBarometric Pressure: ");
  Serial.print(p);
  Serial.println("\n");

  Serial.println("Encoding results");
#endif
  lpp.reset();
  lpp.addTemperature(1, t);
  lpp.addRelativeHumidity(2, h);
  lpp.addVoltage(3, v);
  lpp.addBarometricPressure(4, p);

#ifdef RF95_CLIENT_DEBUG
  Serial.print("Sende Sensordaten ");
#endif
  if (manager.sendto(lpp.getBuffer(), lpp.getSize(), data.gateway_addr))
  {
#ifdef RF95_CLIENT_DEBUG
    Serial.print("OK");
#endif
    manager.waitPacketSent();
  }
#ifdef RF95_CLIENT_DEBUG
  Serial.println("Going to sleep...");
#endif
  digitalWrite(DONE_PIN, LOW);
  digitalWrite(DONE_PIN, HIGH);  
}

I

Start at the beginning.

Write the simplest sketch possible that just uses the TPL5110 to put the Arduino to sleep, make sure that works before adding all the other hardware and code.