iOS Profile rollout not working

Hello Community

I've the following problem with the NextDNS Profile rollout on iPhones.

The creation of the profile which you can download via https://apple.nextdns.io/?profile=4ad6b2 has worked so far.

Based on the profile a configuration profile was created within intune plus a profile to distribute the certificate.

The rollout of the profiles to an iPhone also works. Within the system settings in iOS, the profile is displayed and selected as DNS.

When surfing or communicating on the iPhone (despite several reboots) the NextDNS entry is not used. The default settings of iOS are still used.

When using the app, everything works as desired, but is not suitable for our scenario, since we have all devices managed remotely.

I ask for a solution or advice here.

Thank you very much!