By default, App Broker will only sync users, computers, and relationships a single time during a given day. Until this information is synced into the App Broker DB, newly created users and computers will not be available as targets for software requests... Of course, you can always use the "sync data now" button under settings->deployment->common in order to force a sync. There is, however, and undocumented approach that you can take, in order to schedule a data sync more frequently.
In App Broker, there is a "Trigger File" mechanism, which App Broker uses to invoke certain tasks which occur on a timer. A trigger file is simply an empty text file, with a very specific name, which will trigger a task in App Broker if the file is dropped into the logs folder. If you create a trigger file named Trigger_StartDataSync, and drop this into the logs folder, then it will force the same data sync to run as that of the nightly data sync. Please note that there is no extension on the file name. To schedule additional sync's all you would need to do is create a small script, which could be invoked by a scheduled task, which would copy this trigger file into the logs folder.
While there are quite a few different triggers in App Broker, only a few would likely be helpful.. The following are some trigger file names, and a brief description of each, which you may find useful, particularly when testing in a Dev environment.
Trigger_CollectionCleanup - Force the collection cleanup process to run.
Trigger_CollectionInsert - Force the collection insert process to run.
Trigger_UpdateStatus - Forces App Broker to connect to the SCCM DB to check the status on pending requests.