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I have a parent with 3 scouts in our pack, and he is not able to see any of them when she logs into Scoutbook. I have confirmed that he has set up an account on my.scouting.org which he has (and says he has to change her password every time he tries to log in). And I also confirmed that he is using the same credentials that he set up in my.scouting.org to log into scoutbook.
This parent has 2 BSA Member IDs (MID). His other MID is 13956249.
I only found one my.scouting.org ID which is attached to MID 137389354. The Scoutbook ID with this MID is connected to all 3 children you posted MIDs for.
He needs to log in with his last name followed by 9999. I was not able to find any other Scoutbook ID or my.scouting.org ID for him, but he does have a common name