Duplicated DKIM Records

You have more than one DKIM signature in your message.
Please enable only one signature, you should let your mail server sign the message and disable DKIM on your Newsletter software.

Signature 1 :

   v=1;
   a=rsa-sha256;
   c=relaxed/simple;
   d=mydomain.com;
   s=default;
   t=1605751409;
   bh=v0PCw6PHtFEI+GSOBRdJL3ZodUqtMBk6xojkM/3MWU8=;
   h=Date:From:To:Subject;
   b=<Some key1 record>

Signature 2 :

   v=1;
   a=rsa-sha256;
   c=relaxed/simple;
   d=mydomain.com;
   s=default;
   t=1605751407;
   bh=v0PCw6PHtFEI+GSOBRdJL3ZodUqtMBk6xojkM/3MWU8=;
   h=Date:From:To:Subject;
   b=<Some key 2 record>

How can I fix this?

more information needed, how are you sending the emails?

I tested this message using Round Cube and PHP mailer.

you need to check maillogs or check with experienced sysadmin or cwp support

Ok the problem seems to be missing DKIM entry in my DNS configuration when sending mails using PHP Mailer and Duplicate entry when using Round Cube, but I don't know where to find this public key to add it to my DNS TXT entry nor where the signature is duplicated. No need to pay for external sysadmin, but some help in this "help forum" will be welcomed and usefull.

dkim configuration is in /etc/opendkim
or you can check with cwp support

Ok thanks for your clues, it was already repaired yesterday! But for today, for some reason after "yum update" into CWP all server went down! Only showing test page. What is wrong now, where is my CWP installation?

After
$service cwpsrv start

Now RoundCube doesn't exists!
The requested URL /roundcube/ was not found on this server.

After Rebuilding Apache everything got normal.