Adding a marker image to Google Maps on IOS Objective-C app

I have a map to show directions. I am able to tap on a direction to view an annotation with the instructions but what I am trying to do is add a marker to the directions coordinates. Here is the code I am currently using:

-(void) getDirectionsFromStart: (CLLocation*) start toEnd: (CLLocation*) end
{

NSString *mapDir = [NSString stringWithFormat:@"http://maps.googleapis.com/maps/api/directions/json?origin=%f,%f&destination=%f,%f&sensor=false", start.coordinate.latitude, start.coordinate.longitude, end.coordinate.latitude, end.coordinate.longitude];
if ([self.directionsArray count] == 0) {

//parse the string response and then draw the points on a map
    NSError *error;
    NSString *response = [NSString stringWithContentsOfURL:[NSURL URLWithString:mapDir] encoding:NSUTF8StringEncoding error:&error];
    if (response == nil) {
        NSLog(@"Google Maps error: %@", [error localizedDescription]);
        NSLog(@"Google Maps recovery: %@", [error localizedRecoverySuggestion]);
        //[self getDirectionsFromStart:nil toEnd:nil];
    }
    self.directionsArray = [gMapsJsonDirectionsParser parseJsonToMapDirections:response];
}
for (gMapsJourneyLeg *leg in self.directionsArray) {
    @autoreleasepool {

    self.directionsHeader.text = [NSString stringWithFormat:@"To %@ Taking: %@", leg.end_address, leg.duration.text];
    for (gMapsStep *step in leg.steps ) {
        MKPolyline *polyLine = [gMapsJsonDirectionsParser polylineWithEncodedString:step.polyLine];
        MKPolylineView *line = [[MKPolylineView alloc] initWithPolyline: polyLine];

        line.fillColor = [UIColor blueColor];
        line.strokeColor = [UIColor blueColor];
        line.lineWidth = 5;
        [self.mapView addOverlay:polyLine];
        //[self.mapView setVisibleMapRect:polyLine.boundingMapRect];
        //map point code
        MKPointAnnotation *point = [[MKPointAnnotation alloc] init];
        point.coordinate = step.end_location.coordinate;
        point.title = step.htmlInstructions;

        [[self.mapView viewForAnnotation:point] setTag:1];
        UIImage *image = [UIImage imageNamed:@"marker_red.png"];
        [[self.mapView viewForAnnotation:point] setImage:image];

        [self.mapView addAnnotation:point];
    }
    }
}

[self.tableView reloadData];
}

To be clear, the annotations and polyline are both fine it's just the marker is never shown.

Base on the code in the Google Docs for Markers:

Here is the sample code for adding markers with custom image.

CLLocationCoordinate2D position = CLLocationCoordinate2DMake(51.5, -0.127);
GMSMarker *london = [GMSMarker markerWithPosition:position];
london.title = @"London";
london.icon = [UIImage imageNamed:@"house"];
london.map = mapView_;

May be you have not set the GMSMarker *london = [GMSMarker markerWithPosition:position]; that is why your marker is not visible. Kindly check the marker without a custom image if it will show up, if not try adding the markerPosition property.