The best process servers place a phone call to the servee any time that they do not receive an answer at the door. If someone is not home, give them a call! Be open and honest, introduce yourself, and inform them you are a courier with legal documents for them. Ask them for a good time to reach them. And, of course, log the details of the phone call in ABC Mobile.
After that, take whatever step makes the most sense. Did you learn that the servee still resides at the indicated address? Make attempts when they will be home, or meet them somewhere convenient. If they tell you that they moved, submit a Bad Address event in ABC Mobile.
Note: If you have not been provided with a phone number, do not seek one out. If your local regulations prohibit the use of phone calls in regard to service of process, do not place a phone call.