Unable to read server backup directory

Hi,

I am getting problem when try to restore my backup Zimbra from ZxBackup smartscan or migration tools. when try to restore, i am always getting the following error

Operation requested by: zimbra

ZeXtras Suite Version: 2.4.12
commit: b9b40103e773cdcfe197e3e1618dbcda4e3cafcf

Zal Version: 1.12.0
Zal commit: b9b40103e773cdcfe197e3e1618dbcda4e3cafcf
Zimbra version: 8.7.11_GA_1854 20170531151956 20170531-1546 FOSS

- exception -
com.zextras.lib.Error.UnableToReadBackupDirectoryError: Unable to read server backup directory
at com.zextras.backup.ZEBackupServer.getBackup (ZEBackupServer.java:341)
at com.zextras.op.backup.ZEExternalRestoreOperation.doOperation (ZEExternalRestoreOperation.java:577)
at com.zextras.op.ZEOperation.exec (ZEOperation.java:770)
at com.zextras.op.LegacyOperationProxy.exec (LegacyOperationProxy.java:83)
at com.zextras.op.StatefulOperationImpl.exec (StatefulOperationImpl.java:117)
at com.zextras.op.OperationStarterActivity.run (OperationStarterActivity.java:45)
at com.zextras.lib.activities.ActivityThread.run (ActivityThread.java:122)

I've give 777 permission for backup folder. But, still cannot restore my backup

Old Zimbra : ZCS 8.6 OSE
New Zimbra : ZCS 8.7.11 OSE

Thanks