关于微信登录返回的问题，求大神解答

[倔强的孩子气]

想问一下，微信登录返回code之后，我拿去请求，测试到返回的data是正常的，但个别用户会出现data为空的情况，显示微信参数错误，是腾讯的问题吗？还是我代码写错了

        NSString *url =[NSString stringWithFormat:@"https://api.weixin.qq.com/sns/oauth2/access_token?appid=%@&secret=%@&code=%@&grant_type=authorization_code",wxappid,wxAppSecret,code];
        
        NSURL *zoneUrl = [NSURL URLWithString:url];
 
        NSString *zoneStr = [NSString stringWithContentsOfURL:zoneUrl encoding:NSUTF8StringEncoding error:nil];
        
        NSData *data = [zoneStr dataUsingEncoding:NSUTF8StringEncoding];
        
        if (data) {
            
            NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];
            
            
            NSString *access_token = [dic objectForKey:@"access_token"];
            NSString *openid = [dic objectForKey:@"openid"];
            
            return;
            
        }
        
        [Utility showWarningContentString:@"微信参数错误"];