Zoho Projects API, tasklist not working?

Zoho Projects API, tasklist not working?

I am trying to get tasklist information from the Zoho Projects API, but all requests on the tasklists object return a 400 error (Bad Request).

I'm using the link returned from a GET projects request:

https://projectsapi.zoho.com/restapi/portal/<<portalid>>/projects/<<projectid>>

  1.       "link": {
  2.             "tasklist" : {
  3.                   "url" : "https://projectsapi.zoho.com/restapi/portal/<<portalid>>/projects/<<projectid>>/tasklists/"
  4.             }
  5.       }

I had also tried requesting a specific tasklist (with the ID retrieved from a GET tasks request), with the same result.

The JSON response is an error, code 6500 ("General Error").