Third party ticket agency Viagogo is pressuring customers by pretending the events are sold out, and only they still have a few tickets left. These of course are terribly overpriced, and it wasn't true in the first place that the events were sold out.
It seems that they also sold "tickets" online that weren't even on the market yet, and sent customers a worthless piece of paper.
Anyone affected by this might also want to check out this Facebook group. (Some of the other sources are in German only, sorry.)