Maps available for selection as background maps in Quickstart
If you tap the Select map button in Quickstart you can choose a map for your Quickstart course from the list of maps given. If you are wondering why some maps for courses you have downloaded, including Check Sites ones, don't appear in the list, this is because by default published course maps have Reuse = No set as an attribute of the map, and Check Sites maps always have Reuse=No set. LAs can change the reuse flag to Yes when they publish a course, but if you wish to reuse a Check Sites map you have to ask the publisher of the Check Sites event for a copy of the KMZ file, and then import it into your phone to make it available for reuse.
Note that at the moment the info message against the Select Maps option in Quickstart says that all downloaded maps are available, but that isn't currently the case, and the system is working as designed; it's the message that's currently wrong, not your Check Sites course or the system!