PREL Status on a Network

[mrshogue]

We recently ran into an issue where we couldn't receive materials in ZPPO because it said the network activity wasn't in REL status. I verified the network activity was in REL status, BUT the network was in PREL status. I am not sure what the value of the PREL status is in general. We also have never ran into this issue of charges not being able to be incurred on a REL activity because the network was in PREL status. Nevertheless, we changed the status of the network to REL and everything worked fine.
Anyone run into this same problem? Can anyone explain to me what the value of REL is? Why can't the network status go from CRTD to REL if there are multiple activities attached?