Somehow the payments are going through. wordpress (digimember) creates the wordpress-accounts for the customers. But digistore doesn´t get the information about the password and the username which the customers need to log in.
The spreadshop ist not affected and has nothing to do with digistore.
The digimember-support told me to disconnect an reconnect digimember and digistore, which didn`t work out. Teh last answer I got was
"Sollte das auch nicht gehen, teile den Link vom Ausgangsserver dem Support von Ezoic mit, dass seit der Umstellung dieser Link nicht mehr erreichbar ist."