404 error when creating a timesheet in ZoHo Projects

404 error when creating a timesheet in ZoHo Projects

I'm trying to create a time log for a task in ZoHo Projects (aka Add Time Log for a Task).
1. I have create access (oAuth sets authority to ZohoProjects.timesheets.ALL)
2. I am using php and cURL
3. I am sending a POST request to  https://projectsapi.zoho.eu/restapi/portal/200XXXXXXXX/projects/XXXXX000000053053/tasks/XXXXX000000196860/logs/ (I've replaced the actual IDs with some Xs)
4. The http header includes my access token -- this is all in order, as I can use it to make other requests
5. The cURL POSTfields are set to:  
date=06-03-2019&hours=01:00&bill_status=Billable&notes=My+note
6. My php code is similar to the given example (and other requests work fine)

However, I get the response "The requested URL returned error: 404 "

Can anyone suggest what I'm doing wrong?