>Can you share the solution?
>
>>Never mind, solved the problem.

The class had several simple properties and a list of a different class. All I needed to do is to add a map for that class as well, e.g. these 4 lines were enough:

Mapper.CreateMap<InvoicesToPayViewModel, InvoicesToPay>();
            Mapper.CreateMap<InvoicesToPay, InvoicesToPayViewModel>();
            Mapper.CreateMap<TransactionObjectViewModel, TransactionObject>();
            Mapper.CreateMap<TransactionObject, TransactionObjectViewModel>();

My original try was just 2 last lines and therefore it was failing.