ESP8266 WiFi doesn't reconnect

Question

I've been reading this post while trying to optimize the usage of the WiFi module on my ESP8266.

My main goal was to be able to connect/disconnect (respectively turn on/off) the WiFi module so I can optimize electricity consumption of the chip (I am trying to solar power it).

So, the way I integrated the proposed solution is as follows as I am no where calling deepSleep:

#include <RelayModule.h>
#include <ESP8266WIFI.h>
#include <rdm6300.h>
#include <string.h>
#include <ctime>

extern "C" {
    #include "user_interface.h"  // Required for wifi_station_connect() to work
}
/*...*/
#define RFID_PIN 13
#define RELAY_PIN 10
#define FPM_SLEEP_MAX_TIME 0xFFFFFFF
#define RELAY_OPEN_DURATION 6

RelayModule relay(RELAY_PIN);
Rdm6300 rdm6300;

int relayTurnedOnAt = 0;

void WiFiOn();
void WiFiOff();

void connectToWifi() {
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) 
  {
     delay(500);
  }
}

void setup() {
  connectToWifi();
  rdm6300.begin(RFID_PIN);
  /*...*/
}

void openFrontDoor() {
  WiFiOn();
  if(relay.isOff()){
    relay.on();
    relayTurnedOnAt = time(0);
  }

  /*Perform some business logic which makes a reference to Services hosted on the Internet*/
}

void lockFrontDoor() {
  relay.off();
  WiFiOff();
}

void loop() {
  // RFID TAG WAS SCANNED
  if (rdm6300.update()){ 
    openFrontDoor();
  }

  if (relay.isOn() && abs(time(0)-relayTurnedOnAt) > RELAY_OPEN_DURATION)
    lockFrontDoor();
}

void WiFiOn() {
    wifi_fpm_do_wakeup();
    wifi_fpm_close();

    //Serial.println("Reconnecting");
    wifi_set_opmode(STATION_MODE);
    wifi_station_connect();
}


void WiFiOff() {
    //Serial.println("diconnecting client and wifi");
    //client.disconnect();
    wifi_station_disconnect();
    wifi_set_opmode(NULL_MODE);
    wifi_set_sleep_type(MODEM_SLEEP_T);
    wifi_fpm_open();
    wifi_fpm_do_sleep(FPM_SLEEP_MAX_TIME);
} 

The problem here is that once disconnected, I can not get the WiFi module connected back. I need to reset/restart the chip and then I get connected to the internet once again. I would like to be able to fully disable the module when not needed (and save power) and when I need it to submit some stuff to the internet - wake it up, do the job and then bring it back to suspended mode.