Where I can see the ms sql server backup job report?

All job reports can be found in "Job report" window , just mouse right click on a job node , you'll see all this job's history report . see following file attached. if you can not see the latest reprt , please click "Refresh" button .

All reports are clean after 60 days , you can also attach a copy of reprot to the notify email , see following file attached.
Scheduled job's report is created DataBK Job Scheduler service running account, if this account is different from the backup manager running account, the backup manager may have not enough privilege to access the file or is delay updated to the backup manager running account, but you can find all job logs in the configuration directory, just click File->Open configuration dir ... menu and open JobReports subdirectory.