Yes, otherwise you lose by default. You can only explain what happened and hope for the best. But only explain if the court asks. Worst comes to worst, the court will dismiss and you will have to start over.
You must fully understand 562A of the Iowa Code,otherwise you need to hire a lawyer.
Chances are great if your tenants do not show. It is likely they will not show. When you are awarded the judgement you should immediately begin to garnish wages if your state law provides for it. At some date in the future your tenants may come out of the fog and ask to "settle" for a lesser amount. They will offer to settle because the pinch of a poor credit rating is catching up with them. Be prepared to say no and get off the phone.