I have successfully deployed my timer job and it appears in the Central Admin but I cannot find it in Job Definitions or Running Jobs either in the Monitoring option of Central Admin. What could be the cause of this problem??
I think you have only deployed the solution (wsp) file of the timer job. You will also need to activate the feature for your timer job.
Go to the Site collection features of your Web-application and Activate your timer job feature from there.
This should start showing your timer job in the list of Job Definitions in the Central Administration.
I hope this helps.
After deploying solution, go to your solution scope level (Web application/Site Collection) and activate feature. Then on SharePoint Server restart the SharePoint Timer Service.