Groovy expression to send email when sr is not resolved and sr creation time passes 12 hours i

We have a requirement that:

1. We need to send a reminder email notification to HRHD Agent when a HR Help Desk Request is unresolved, below is the scenerio:
   1. We need to send email notification to Agent after 12 hours (assume) when HR Help Desk Request is created and SEV is High
   2. We need to send email notification to Agent's Manager if the request is not resolved withing 24 hours (assume) when SEV is High

I am trying to achieve this through Object Workflow within Application Composer, I have used below Groovy Expression to trigger the email to satisfy the conditions, but it didn't work.