In order to view you AMEX transactions you will need to switch the Merchant Account view
Select the 'Merchant Accounts' tab to view the AMEX Transactions and select the merchant ID for your AMEX account
Alternatively while viewing the 'Transactions' tab if you use the 'Advanced Filters' tools you will be able to tick 'Toggle All Accounts' followed by selecting the appropriate time frame (e.g. This Month) and once set click 'Filter Transactions'. This will load all of the Transactions across the Merchant Accounts on one page.