Cann’t edit theme functions.php file.

Hi,

I have a site hosted with GoDaddy but not able to edit the child theme functions.php file. I am getting following error –

Unable to communicate back with site to check for fatal errors, so the PHP change was reverted. You will need to upload your PHP file change by some other means, such as by using SFTP.

I read other forums and added error log code, but I am not getting any referral URL’s.
I get this –

[15-Jan-2018 19:00:07 UTC] PHP Notice:  Constant WP_MEMORY_LIMIT already defined in /home/oym0bzp2qcbw/public_html/wp-config.php on line 115
[15-Jan-2018 19:02:12 UTC] Starting edit check
[15-Jan-2018 19:02:12 UTC] Body:
[15-Jan-2018 19:02:12 UTC] 
[15-Jan-2018 19:10:07 UTC] Starting edit check
[15-Jan-2018 19:10:07 UTC] Body:
[15-Jan-2018 19:10:07 UTC] 

I have put the error log code in file.php –

error_log( 'Starting edit check' );
error_log( 'Body:' );
error_log( $body );

if ( is_wp_error( $r ) ) {
  error_log( 'Connection failed' );
  error_log( var_export( $r, true ) );
} else {
  error_log( 'Connection created');
}

		$loopback_request_failure = array(
			'code' => 'loopback_request_failed',
			'message' => __( 'Unable to communicate back with site to check for fatal errors, so the PHP change was reverted. You will need to upload your PHP file change by some other means, such as by using SFTP.' ),
		);

I also called GoDaddy and they say it’s WordPress issue.
Please help.
Thanks.