Why am I not seeing any Dibs?
1) Make sure you are logged in with the account that was used to register your skater as only the registrants account is able to view and claim Dibs.   If you are the non-registering parent, you can request the registering parent to attach you to the skaters profile (see PDF document in the "Add a second email to an account" tab).
2) It could be that all Dibs have been claimed at the moment and you will need to check back for the next batch of volunteer shifts to be uploaded.

What if I have multiple skaters and all of my completed hours are under only 1 skater? 
You should try and balance out the hours you claim between 2 skaters (7.5 each), but if the 15 hour total for your family is met, you are good to go.