Thank you @aspirin624!
I will try your approach within the next few days.
Until now I was using the same addesses for Sygic, TomTom Go 1.6 and 1.7* and it was working.
This new TomTom app does no accept these addresses. I also realized that the postage-code database for my country (Singapore, where every building has a unique postage code) is wrong.