The key here, and what I have told parents with similar questions, is the youth needs to want, and own this situation. Yes, I assume your in a Troop that's running mostly right, I say mostly because no troops perfect. The scout needs to either bring this up in his up and coming SMC, or go to the "youth" responsible for Den Chiefs in your troop. As a parent, your role is to point your scout in the correct direction, and let him handle this. If and when your scout has issues with this seek direction form the CC.
To answer why I say the scout should deal with the ASPL, that's because the SPL is directly responsible for the ASPL, PL's, and Guide only (found in the SM's Handbook, Senior Patrol Leaders Handbook, and Patrol Leaders Handbook). The ASPL is responsible for he balance of the officers (the administrative officers).
Where you may be going with here is Den Chiefs aren't actually defined as part of either officer group, and BSA (the last time I checked) recommends they be supervised by an ASM. I don't run, or teach the program that way (which doesn't make me right). In our unit, and the others I've worked with, the ASPL is responsible for Den Chiefs, but they answer to the Den Leader they work with.