Ola Hallengren - DatabaseBackup - LOG Unable to open Step output file. The step failed
It turns out that the person migrated the jobs from old server to new server edited the jobs manually.

One of the edit was to "Output File: (Job Step properties--&gt;Advanced)" 
this was set to default log location C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\Log on old server.

On the migrated server it was edited to "F:\SQLAgentLog\Log\" where the directory Log did not exist. (that person missed deleting the Log text in the path)

On the other jobs (FULL and DIFF) the text Log had been removed so it was set like this "F:\SQLAgentLog\" and these both were working fine!