// https://wokwi.com/projects/359387026908041217
// https://forum.arduino.cc/t/obtaining-the-maximum-element-from-an-array/1102930

int Array [10];  //... you need to, at some point, make room for N elements
int i;

void setup() {
  Serial.begin(9600);
}

//... the arguments can have any names you'd like
int maximum (int anArray[], int n) {
  int max = 0;

  Serial.println("in the maximum function:");

  for (int i = 0; i < n; i++ ) {
		if ( anArray[i] > max)	{
			max = anArray[i];
		
      Serial.print("    The (new) max value is: ");
      Serial.println(max);
    }
	}
//... you promised to return ann int, but failed to
  return max;
}

void loop() {
  for (int i = 0; i < 10; i++) {
//... statement does... absolutely nothing
//    Array [i];

//... check random - the upper limit is not returned!
    int num = random (0,10);  //... random number 0..9 inclusive

    Array [i] = {num};
    Serial.print(Array[i]);
    Serial.print(",");
    delay(150);   //... life to short!
  }

//... I moved this print statement. Sue me.
  Serial.println("       Full Array ");

//... this is a declaration. it does not execute any code
//  int maximum (Array, 10);
//
// you want to actually call the function you wrote, and assign the returned value value.

  int theMaximum = maximum(Array, 10);

  Serial.print("         maximum from function call ");
  Serial.println(theMaximum);

  delay(300);  //... life too short!
}