Mailbox service installation error Exchange 2013 : Mailbox role

Hi all, I'm getting the following error at Setup of Mailbox role:Mailbox service

Error:
The following error was generated when "$error.Clear(); 
          if ($RoleIsDatacenter -ne $true)
          {
            if (Test-ExchangeServersWriteAccess -DomainController $RoleDomainController -ErrorAction SilentlyContinue)
            {
              $sysMbx = $null;
              $name = "SystemMailbox{bb558c35-97f1-4cb9-8ff7-d53741dc928c}";
              $dispName = "Microsoft Exchange";
              Write-ExchangeSetupLog -Info ("Retrieving mailboxes with Name=$name.");
              $mbxs = @(Get-Mailbox -Arbitration -Filter {name -eq $name} -IgnoreDefaultScope -ResultSize 1 );
              if ($mbxs.Length -eq 0) 
              {
                Write-ExchangeSetupLog -Info ("Retrieving mailbox databases on Server=$RoleFqdnOrName.");
                $dbs = @(Get-MailboxDatabase -Server:$RoleFqdnOrName -DomainController $RoleDomainController);
                if ($dbs.Length -ne 0) 
                {
                  Write-ExchangeSetupLog -Info ("Retrieving users with Name=$name.");
                  $arbUsers = @(Get-User -Filter {name -eq $name} -IgnoreDefaultScope -ResultSize 1);
                  if ($arbUsers.Length -ne 0) 
                  {
                    Write-ExchangeSetupLog -Info ("Enabling mailbox $name.");
                    $sysMbx = Enable-Mailbox -Arbitration -Identity $arbUsers[0] -DisplayName $dispName -database $dbs[0].Identity;
                  }
                }
              }
              else
              {
                if ($mbxs[0].DisplayName -ne $dispName )
                {
                   Write-ExchangeSetupLog -Info ("Setting DisplayName=$dispName.");
                   Set-Mailbox -Arbitration -Identity $mbxs[0] -DisplayName $dispName -Force;
                }
                $sysMbx = $mbxs[0];
              }

              # Set the Organization Capabilities needed for this mailbox
              if ($sysMbx -ne $null)
              {
                # We need 1 GB for uploading large OAB files to the organization mailbox
                Write-ExchangeSetupLog -Info ("Setting mailbox properties.");
                set-mailbox -Arbitration -identity $sysMbx -UMGrammar:$true -OABGen:$true -GMGen:$true -ClientExtensions:$true -MailRouting:$true -MaxSendSize 1GB -Force;
              }
              else
              {
                Write-ExchangeSetupLog -Info ("Cannot find arbitration mailbox with name=$name.");
              }
            }
            else
            {
              Write-ExchangeSetupLog -Info "Skipping creating E15 System Mailbox because of insufficient permission."
            }  
          }" was run: "Database is mandatory on UserMailbox.".

Error:
The following error was generated when "$error.Clear(); 
          if ($RoleIsDatacenter -ne $true)
          {
            if (Test-ExchangeServersWriteAccess -DomainController $RoleDomainController -ErrorAction SilentlyContinue)
            {
              $sysMbx = $null;
              $name = "SystemMailbox{bb558c35-97f1-4cb9-8ff7-d53741dc928c}";
              $dispName = "Microsoft Exchange";
              Write-ExchangeSetupLog -Info ("Retrieving mailboxes with Name=$name.");
              $mbxs = @(Get-Mailbox -Arbitration -Filter {name -eq $name} -IgnoreDefaultScope -ResultSize 1 );
              if ($mbxs.Length -eq 0) 
              {
                Write-ExchangeSetupLog -Info ("Retrieving mailbox databases on Server=$RoleFqdnOrName.");
                $dbs = @(Get-MailboxDatabase -Server:$RoleFqdnOrName -DomainController $RoleDomainController);
                if ($dbs.Length -ne 0) 
                {
                  Write-ExchangeSetupLog -Info ("Retrieving users with Name=$name.");
                  $arbUsers = @(Get-User -Filter {name -eq $name} -IgnoreDefaultScope -ResultSize 1);
                  if ($arbUsers.Length -ne 0) 
                  {
                    Write-ExchangeSetupLog -Info ("Enabling mailbox $name.");
                    $sysMbx = Enable-Mailbox -Arbitration -Identity $arbUsers[0] -DisplayName $dispName -database $dbs[0].Identity;
                  }
                }
              }kipp
              else
              {
                if ($mbxs[0].DisplayName -ne $dispName )
                {
                   Write-ExchangeSetupLog -Info ("Setting DisplayName=$dispName.");
                   Set-Mailbox -Arbitration -Identity $mbxs[0] -DisplayName $dispName -Force;
                }
                $sysMbx = $mbxs[0];
              }

              # Set the Organization Capabilities needed for this mailbox
              if ($sysMbx -ne $null)
              {
                # We need 1 GB for uploading large OAB files to the organization mailbox
                Write-ExchangeSetupLog -Info ("Setting mailbox properties.");
                set-mailbox -Arbitration -identity $sysMbx -UMGrammar:$true -OABGen:$true -GMGen:$true -ClientExtensions:$true -MailRouting:$true -MaxSendSize 1GB -Force;
              }
              else
              {
                Write-ExchangeSetupLog -Info ("Cannot find arbitration mailbox with name=$name.");
              }
            }
            else
            {
              Write-ExchangeSetupLog -Info "Skipping creating E15 System Mailbox because of insufficient permission."
            }  
          }" was run: "Database is mandatory on UserMailbox. Property Name: Database".

*Notes

-the Account is Enterprise Admin.

-IPv6 is Enable for AD.s & Exchange Servers

Any advice please !!!