ReadyApi error running in Azure Devops

We have ReadyApi running tests as part of an Azure Devops pipeline. The Devops agent is self-hosted on a Windows Server 2019. Agent is running as a Windows NT service with an account that is local administrator. We are using ReadyApi vers. 3.59.0

When running the test, it fails with:

ERROR [SoapUI] An error occurred
The application does not have desktop access, but this program performed an operation which requires it
JxBrowser cannot be initialized. The default Java browser will be used instead.
java.awt.HeadlessException: 
at sun.java2d.HeadlessGraphicsEnvironment.getDefaultScreenDevice(HeadlessGraphicsEnvironment.java:58

The error happens in a step where we contact a https ADFS website.

If I run the self-hosted Devops agent in a command prompt, then the test runs fine. Does anyone have an idea on how to fix this? 

Best regards
Soren