arrears not collecting

EE is active.  They have an arrears balance for a Disability Plan.  The arrears are not being collected from their pay.

. They do not have any Max Set Override set up

. They are getting regular paycheques

. The arrears are on the same empl rcd/benefit record as their pay

. Their ABBR is correct

We have other employees with arrears in this same plan, and the arrears are being collected on pay.

I have looked at every data detail I can think of to see a difference between this EE and the ones that are getting arrears collected and cannot find any difference.