Hi @Thirunavukkarasu ,
You have a similar issue as this case: sql-server-transaction-log-shipping-does-not-restore-trn-files
So please try similar solution as next:
At the bill DB properties on primary server SQL1, the transaction log replication setting to SQL2 was removed. The wizard also removed the copy and restore jobs at SQL2. The replicated bill DB at SQL2 was removed manually. The transaction log shipping configuration was deactivated at the bill DB on SQL1. All files in the LSBackup and LSRestore folders were deleted. The maintenance plan was deactivated.
Next the transaction log shipping configuration was redone, as described above. Again the target database at SQL2 was initialized by a full backup of the bill DB from SQL1. Finally the secondary server SQL2 was able to restore the .trn files.
More information: log-shipping-in-sql-server-2008
BTW, quote from this doc.: end-of-support-for-sql-server-2008-and-sql-server-2008-r2
...
Customers who use SQL Server 2008 or SQL Server 2008 R2 products and services should upgrade to the latest version of SQL Server on-premises or re-host to Azure SQL Database Managed Instance, a version-less offering that eliminates the need for future upgrades. Or, migrate to Microsoft Azure virtual machines to take advantage of 3 additional years of Critical security updates at no additional charge and modernize when ready.
...
BR,
Mia
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