Show a cell from Google Sheets on WordPress using PHP

I found this code through a blog. I am attempting to return a single cell from Google Sheets. Forms will be completed on my WordPress website. The cell sums these forms. I want to return the sum from the Google Sheet. I have followed every step (correctly, I think!). It does not work. Short code just shows up on the website. It does not actually return the value in the single cell in Google Sheets. Can someone look at this and tell me what might not be working? Thanks!

function sheet_value_shortcode($atts) {
		$API = 'AIzaSyClwl_TDt4HzBXuGhgiYqmrAEyDZnPGmzE';
		$google_spreadsheet_ID = '1lbaeLarSa41rL-4dLin6I4oj5_X8SXzxlDsGyrnhJqw';
		$api_key = esc_attr( $API);

		$location = $atts['location'];

		$get_cell = new WP_Http();
		$cell_url = "$google_spreadsheet_ID/values/$location?&key=$api_key";	
		$cell_response = $get_cell -> get( $cell_url);
		$json_body = json_decode($cell_response['body'],true);	
		$cell_value = $json_body['values'][0][0];
		return $cell_value;
add_shortcode('get_sheet_value', 'sheet_value_shortcode');

Here is where I found the code:

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