Okay, it's getting really stange. Still waiting for the next response from travelstart (don't expect it until weekend). No problem at all...
But I'm someone who likes to sneak around. So I tried the original booking reference at Eurowings homepage (the airline operating the cancelled flight) and I expected to get an error message. But no no no... I get so see a valid booking for the flight from Nuremberg to Dusseldorf, but instead departing 12:20 (the original flight was 18:00 that was moved to 17:00 and is now cancelled). The strange thing is that when checking the booking I get to see a different booking reference. This booking reference is unknown to ANA system. So maybe there's no need for re-booking by the OTA because there's still a valid flight but ANA didn't get a notice from Eurowings?
I'm getting confused more and more...