Unable to add database copy for DR mailbox server

Hi,

Recently i configured DR for our Exchange infra with 2 CAS server and 2 Mailbox server. For DR cas server i created a separate NLB as drmail.domain.local. And add the DR mailbox server in Existing DAG.  Now while trying to add a active database copy its showing following error. 

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The seeding operation failed. Error: An error occurred while performing the seed operation. Error: Failed to open a log truncation context to source server 'DC-MAILBOX-02.domain.local'. Hresult: 0xc7ff07d7. Error: Failed to open a log
truncation context because the Microsoft Exchange Information Store service is not running. [Database: MBXDB03,
Server: DRC-MAILBOX-01.domain.local]
    + CategoryInfo          : InvalidOperation: (:) [Update-MailboxDatabaseCopy], SeedInProgressException
    + FullyQualifiedErrorId : [Server=DC-MAILBOX-02,RequestId=3bdf9fa0-7f18-4f05-a18e-f2d61369bcb7,TimeStamp=17-07-201
   6 10:00:48] 5C92F4F2,Microsoft.Exchange.Management.SystemConfigurationTasks.UpdateDatabaseCopy
    + PSComputerName        : dc-mailbox-02.domain.local

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And when i try to verify the same Fail over cluster validation found the following error.

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An error occurred while executing the test.
There was an error getting information about the operating systems on the node.

Unable to connect to DRC-MAILBOX-01.domain.local via WMI. This may be due to networking issues or firewall configuration on DRC-MAILBOX-01.domain.local.

The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)

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 And cluster name is also not showing in Fail over cluster manager while try to connect to a cluster its givs the same error RPC server is unavailable. 

But from ECP which view the DAG members status its showing operational. Please help me to find a solution .

Thanks in advance.