Welcome! This forum has a treasure trove of great info – Scouters helping Scouters! Just a heads up, though - all content, information, and opinions shared on this forum are those of the author, not the BSA.
I have two Scouts from another unit that are going to be den cheifs for our pack.
We have went through the entire process and I even have emails from national confirming they are approved and need to be added to Dens, yet they are not in any of my roster in myscouting or Scoutbook plus.
I checked there because of the recent updates. Just so everyone is aware, I am a super user of Scoutbook Plus and My Scouting. I use it for a Pack, Troop, and Ship being the one to train new parents, Scouts, and leaders on how to use it. And yes I have also went and clear my cache. It is small issues like this that you have to spend 2 hours in a forum to get anywhere. I am trying to not be condesceding, but it is so difficult with some of the ridiculous answers you get from fellow Scouters.
One the second one it seems to me the scouts Troop never accepted the email invite, that would have made a den chief position in SB. There is none, and there is no closed one for the scout.
I think I would start the process again to see if something was missed. Pack invites (Add Den Chief) > Troop gets email asking to accept > Troop accepts > Then Pack can assign to the den
I hate all the steps and SUAC has complained on them, but it is where we are today.