Windows 2012 Domain Controller NETLOGON error

We have Sonicwall firewall user authentication System active since last two months.
We have Windows 2012 Active directory server setup with around 1400 user account created.
These accounts were created by using following PowerShell scripts

Import-Module ActiveDirectory 
#Import CSV 
$csv = @() 
$csv = Import-Csv -Path C:\Users\Administrator\Desktop\"College User Ac Password   Details"\FE\civil.csv
FOREACH ($Person in $csv) {
  $name = $Person.UserName
  $displayname = $Person.Name
  $path = "OU=here,DC=comp,DC=com"
  $password = $Person.Password
  $enabled = $True
  $changePW = $False
  $description="CIVIL"
  new-ADUser -SamAccountName $name -Name $name -Description $description -DisplayName $displayname -Path $path -AccountPassword (ConvertTo-SecureString $password -AsPlainText -force) -Enabled $enabled -ChangePasswordAtLogon $changePW -PassThru

}

Above script reads an CSV file with username and passwords and create user accounts on Active Directory.

But since today we are facing issue during authentication process.
We are unable to logon to Directory server. When Sonicwall firewall tries to authenticate an user, it logged-out same user.
When I checked Event logger on Windows Active Directory server it shows following message.

 The dynamic registration of the DNS record 'ForestDnsZones.comp.com. 600 
 IN A 192.168.0.12' failed on the following DNS server:  

 DNS server IP address: (removed)
 Returned Response Code (RCODE): 5 
 Returned Status Code: 9017  

 For computers and users to locate this domain controller, this record must be registered in DNS.  

 USER ACTION  
 Determine what might have caused this failure, resolve the problem, and initiate   
 registration of the DNS records by the domain controller. To determine what might have 
 caused this failure, run DCDiag.exe. To learn more about DCDiag.exe, see Help and 
 Support Center. To initiate registration of the DNS records by this domain  
 controller, run 'nltest.exe /dsregdns' from the command prompt on the domain 
 controller or restart Net Logon service. Or, you can manually add this record to DNS,
 but it is not recommended.  

 ADDITIONAL DATA 
 Error Value: DNS bad key.

Above log entry talks about DNS issue. But I did non configured any DNS server on this machine.Authentication was working fine for last two months , but suddenly from today we are facing above issue.
Kindly help me out in resolving this issue.

EDIT1

Getting following warning in DNS Server Log

The DNS server is waiting for Active Directory Domain Services (AD DS) to signal that the initial synchronization of the directory has been completed. The DNS server service cannot start until the initial synchronization is complete because critical DNS data might not yet be replicated onto this domain controller. If events in the AD DS event log indicate that there is a problem with DNS name resolution, consider adding the IP address of another DNS server for this domain to the DNS server list in the Internet Protocol properties of this computer. This event will be logged every two minutes until AD DS has signaled that the initial synchronization has successfully completed.