Hi ,
For eg: sapbackup is your backup folder where you intend to store backup files.
I suppose you have defined the backup medium as
Y:\sapbackup ( Where Y:\ is the mapped drive )
Instead you try with this option
\\<IP address of share folder>\spabackup
Ensure share folder ( for eg: sapbackup) has full permission to everyone.
Hope this helps
Regards,
Deepak Kori