I browsed through the YouTube comments of the announcement video and found German comments by the user Latias Latios saying that he/she has contacted the LANXESS arena per email and telephone because the Miku Expo isn't on their schedule yet and they answered that it's not happening and wasn't even discussed. ?!
I know it's not a trustful source and even if he/she did actually contact them, they might have just lied to them because of some private business reason. But there is definitely something fishy. They have concerts for November 2019 scheduled but no Miku Expo in 2018?
Honestly, if this is the reason why ticket sales have been postponed, then they better move the Germany concert to another town instead of waiting for approval. I just want tickets for any show quickly.
So far, I feel like only the Paris show is safe because it's confirmed by Japonismes. If ticket sales are postponed because they have some problems in Cologne or London, then they better only postpone them instead of all the shows. I don't want all of the shows to get delayed until 2019 just because one of the shows has problems. It just looks like one of these "one is guilty - everyone gets punished" situations. I don't wish for any show that has problems to be canceled - oh, God, no - but I just wish they would start selling tickets for the shows that are ready and deal with the problems of the remaining show while people can already secure their tickets.