DeYulia on Cannot connect to ThingSpeak

I'm unable to connect and post data to my ThingSpeak channel.  Data being sent from ESP8266-01S module, using WiFi to access internet.  I can send data to Google Sheets, but not to ThingSpeak.  Something wrong in my connect code.  API is the WRITE API.  Code follows:

[code]
/*
H2O_Flo_WiFi

Measures the flow rate of water flowing through a 3/4-inch PVC pipe using a DIGITEN Hall effect sensor and displaying results on thingspeak.com using an ESP8266-01S
Sensor date wire connected to Uno pin D2
The sensor output is in the form of the duration in milliseconds of a square wave pulse and the relationship to the water flowrate is:

F = 4.8 * Q ( in liters per minute)

ThingSpeak ( https://www.thingspeak.com ) is an analytic IoT platform service that allows you to aggregate, visualize and
analyze live data streams in the cloud.

Documentation for the ThingSpeak Communication Library for Arduino is in the extras/documentation folder where the library was installed.

*/
#include <ESP8266WiFi.h>

String apiKey = "0ZUS9CDG08ZU6VJ2";

#include <ThingSpeak.h>

// WiFi SSD and Password

// char ssid[] = "tracy"
// char password[] = "Mange161"
// char server[] = "api.thingspeak.com"

const char* ssid = "tracy";
const char* password = "Mange161";

const char* server = "api.thingspeak.com";

//Initialize the client library
WiFiClient client;

#include <SPI.h>

void setup() {

pinMode(2, INPUT);

Serial.begin(115200);

delay(1000);

// init done

Serial.println();
Serial.println();
Serial.print("Connecting to ");
Serial.println(ssid);

WiFi.begin(ssid, password);
delay(10000);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.println("WiFi connected");

}

void loop() {

const unsigned long duration = pulseIn(2, HIGH);
//Pulse duration in microseconds

float dursec = duration / 1000000.0;
//Pulse duration in seconds

float pulsefreq = 10.0;

if ( duration != 0 )
{
pulsefreq = 1.0 / dursec;
}
else
{
pulsefreq = 0.0;
}

//Pulse frequency in Hz

float flolit = (pulsefreq / 4.8);
float flolitr = 60.0 * flolit;
//Flow rate in Liters/hour

float flogal = flolitr * .26417;
//Flow rate in Gallons/hour
float flocuft = flolitr * .035315;
//Flow rate in cu ft/hour

if (client.connect(server, 80)) { // "184.106.153.149" or api.thingspeak.com
String postStr = apiKey;
postStr += "&field1=";
postStr += String(flogal);
postStr += "

";

client.print("POST /update HTTP/1.1
");
client.print("Host: api.thingspeak.com
");
client.print("Connection: close
");
client.print("X-THINGSPEAKAPIKEY: " + apiKey + "
");
client.print("Content-Type: application/x-www-form-urlencoded
");
client.print("Content-Length: ");
client.print(postStr.length());
client.print("

");
client.print(postStr);

// 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.

//ThingSpeak.writeField( 255517, 1, flogal, "0ZUS9CDG08ZU6VJ2")

}
client.stop();

delay(600000);
// ThingSpeak will only accept updates every 15 seconds.

}

[/code]