In version 2.9, some features of are moved to other components.
The credits system is now managed by the VirtualMoney component and the invoice system by the Invoicing component.
These two components are included in the silver and gold packs of AdsManager along with PaidSystem.
In order to keep your custom setting and data, you need to transfer your data after installing the new components.
In the configuration page, a link is now displayed just below the title. Clicking on this link will launch the data export.
Note: If you use a credits system, It is possible that the values displayed in virtualMoney is incorrect until you save a virtual currency.
If you don't need a virtual currency system or an invoice system, you can just install the one you need and export data for it. You can also install the other component later if you want.