Eventim Android app not working

Some concert tickets recently purchased from eventim.de seem to be available within the official Eventim app only. No printed ticket, no print at home, no qr code in pdf.
The problem: Eventim app (de.eventim.mobile.app.Android, installed from Aurora store) seems to be incompatible with SFOS app support. After starting the app, it keeps complaining about being offline, however all other Android apps are connected to the internet.
So far no success with the usual workarounmd (flight mode, app support restart). As far I can see, the app does not require any special privileges.
Sony Xperia 10 III, SFOS 4.5, microG

I personally hate buying tickets these days. For eventime I could choose to print the ticket immediately and then print it to pdf.