ACA Manual Entry Missing Control Number

we are adding a few employees on Cobra into the ACA Workbench. We enter all the information into the P08119 and click OK.  For some of our employees they don't get a control number assigned.

We checked for number of months, dependents, etc... and can't find any common variables.

1. Why doesn't the ACA control number create?

2.  Do we need a valid control number to print and create the 1094c

3. How do we had the control numbers if they are required.

Thanks for your help.

Paul