Tenants won't ever answer the door

[Colleen F.]

Three 20 something's  living in the house and  they never answer the door.  I have had 3 separate instances where myself or another tenant knocked on the door and   they would not answer. These were all for various causes.  This last instance was over a blocking vehicle in front of two garages. They would not answer door, or multiple phone calls.  For this instance we issued a lease violation but there were 6 cars and I was ready to have a welfare check done, it was loud door knocking.  Any insight?  Have you had this happen and what have you done? They pay on time  and vehicles we can tow (but should not have to).  I am having trouble though with the behavior.  Any out of the box ideas out there?