I have been dealing with this problem for about a year now with my American Express Bonvoy card.  I think most everyone is having the same problem with the transactions made by additional card holders not showing in quickbooks online even though it clearly shows on the transaction history when you log into American express.  I have tried multiple times to contact support and nobody understands.  You are doing the right thing by manually downloading them.  Hopefully things will change at some point.  Previously we had no issue with transactions downloading even though they were made by other card holders on the account.