Hello @saksham,
OK. If I understand you well, you have Bacula windows client installed, started on the Windows host and you have added it to Bacularis. Although that, you are seeing the error message about not available client.
I would propose to check the firewall setting on the Windows host and open port TCP 9102. This is the port where Bacula client listens by default.
If this will not help, then please check in the process list if the Bacula File Daemon service is started on the Windows host.
Good luck!
Best regards,
Marcin Haba (gani)