NextDNS & Jamf

I want to deploy NextDNS to our devices using Jamf (school). When I try to do this via the app and Apple Managed Configuration, I get an error message when adding an XML file with the following code: "{
  “setup”: true,
  “configuration_id”: ‘my ID’
}“. ”null is not an object (evaluating ‘t.documentElement.nodeName’)"
Furthermore, I have to manually activate the app in the app.
Can you tell me what I’m doing wrong here so that the app is activated automatically and the user cannot deactivate it?
I’ve currently solved this with a profile and the DNS entry, but I’d prefer the app method since, as I’ve read, it offers more options.
Thank you in advance for any assistance.