There was a change to how the default filters were defined in SB+ at one point. I had to manually toggle the filters on my phone before I saw all of our scouts, although it worked just fine on my desktop. You might try having folks reset the filters in the roster to show all of the scouts.
All advancement should be through SB+ for troops now (except for MBCs signing off requirements). The permissions structure was revamped recently-ish, and ASMs do not default to having any permissions for advancement under the new system. Any of the Key 3 or Key 3 Delegates can assign permissions according to the documents linked to from this post in another thread (also shown in a dismissable blue banner at the top of these forums).
https://discussions.scouting.org/t/youth-is-not-eligible-to-earn-this-advancement-error/509427/13
