DKIM did't show in mail header

I have phplist version 3.0.5 on my own server. I tried to add DKIM in the header, the domain pass validation but there’s no DKIM record in the header. I did all from this post, but something wrong and can’t find the problem. Please, give me an advice, what to do.

How this worked for me is explained on my phpList section of my website. This may be of use to you?

I think, the settings are exactly like you wrote. I send mails with SPF successfuly, but can’t add DKIM record. Pass the validations, but there’s no record in header. So, i think that the phplist didn’t add custom header record witch I added.
I found the custum header in class.phpmailer.php and add the DKIM records. You can see it on the picture.

The row with X-MessageID exist in the mail header, but additional DKIM rows, not. Any ideas?

Hard to say without any information, logs or access. There is a few things that might be checked though.
Ensure that DKIM_private file is readable by the php server. Perhaps to write a small php script that opens the file and outputs the first line. If php server fails to read file either by wrong path or access, code will continue without DKIM.
Secondly you might verify what mailer you use. I just use phpmailer and have not been able to test any others.
define("PHPMAILER",1); define("PHPMAILER_PATH",''); define("PHPMAILERHOST",'');

I tested on phpList 3.3.1 and my class.phplistmailer.php is different than yours.
There is no function named PHPlistMailer but this

public function __construct($messageid, $email, $inBlast = true, $exceptions = false)
        parent::SetLanguage('en', dirname(__FILE__).'/PHPMailer/language/');
        $this->addCustomHeader('X-phpList-version: '.VERSION);
        $this->addCustomHeader("X-MessageID: $messageid");
        $this->addCustomHeader("X-ListMember: $email");

	// Test of DKIM
        $this->DKIM_domain = ....
        $this->DKIM_selector = ...
        $this->DKIM_private = ....
        $this->DKIM_passphrase = ....
        $this->DKIM_identity = ....

At last I have heard about people having problem with keys they created from websites when using later versions of phpmailer if the key is created with SHA1 instead of SHA256. phpList 3.3.1 includes version 5.2.22.

Good luck !