SIXT-app on iPhone not working with NextDNS

Dear Forum members,

when I start the SIXT app on my Apple iPhone (IOS 17) having NextDNS profile enabled, the app is starting but does not continue to login screen (remains on showing sixt logo). Even after digging through the NextDNS logs I could not figure out, what the cause for this bahavior is (no specific blocks that I got aware of, just google analytics, Apple metrics as usual).

Can you maybe help me further?