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.
My scout had a multiple application in two different packs. On March 25th, his membership in one of the packs ended. I cannot add him back. When I try, the error message says I have to end his membership in the other pack first. Are scouts no longer allowed multiple memberships?
The note says: DateEnded set by AkelaSBDeltaSync as AkelaExpiryDate < CharterRenewalDate
Honestly, the best option for you would be to log into my.scouting.org > menu > my application. Then, click the multiple button beside your son. When you search for the pack, make sure you include the leading zero because it expects a four digit number.