The resource could not be found when trying to send invitation via api

I’m using postman and trying to send an invitation using the alpha invitation api.

I’m making a post request to https://api.contentful.com/organizations/{organization_id}/invitations. I’ve also set the header to have “Content-Type” = “application/vnd.contentful.management.v1+json”.

I’ve confirmed that the organization id is correct as it works with the other management apis. Any help would be appreciated.