Things to remember while working with sharepoint timer job .

Important Note

Note that, whenever you change the logic or code inside Execute() method, you must restart the Timer service from Services.msc. If you just deploy without restarting service, it will not take your latest updates. So always have practice to restarting the "SharePoint Timer Service" from Services.msc.

If you still face any problem registering or deploying timer job, try uninstalling your assembly and restart the IIS and then deploy again.

To uninstall assembly, in "Run" type "assembly" and press enter. In list of assemblies, you will see the assembly of your project name. Select that and uninstall by right click.

To restart IIS, in "Run" type iisreset and press Enter.