Access to individual accounts is controlled by permissions, which are assigned by the bank. You can see all details for your permissions in the user profile under Rights. For instance, a user who does not have right on AZV (international payments) for a certain account cannot select this account to enter a payment. If you initiated changes in this regard at your bank, for instance by opening new accounts, it will be necessary to update the user profiles.
Do so by marking the desired banks in the Jobs perspective and pressing the F5 key on the keyboard. Alternatively, you can right-click on the desired banks and then select the menu item Refresh by left-clicking in the context menu.
Under General in the preferences you can enable automatic updates of the user profile every time the BL Banking application is started.