User Defined Content journey task

Summary:

Getting hcm content trough REST APIs on User Defined Content journey task

Content (please ensure you mask any confidential information):

I've been working on defining User Defined Content task for a journey following the guide posted here but I can't make it work. In my case the REST API is from HCM, something like this:

https://****/hcmRestApi/resources/latest/absences?q=personId={PersonId};absenceType='Sick Leave'

I have tried basic authentication and integration flag enabled as well but I always get this error:

"Failed with HTTP error code : 401"

Do you have any clue or additional guidance to make it work? Thanks in advanced.