Data Table update - 405 error

Hi. I'm creating a data action to write a new datatable row when a customer selects an IVR option. It works fine in API Explorer using POST when it's an unused key, but when building the Data Action, when POST is selected I receive an HTTP 405 Method Not Allowed message when submitting the same data. if I PUT the data via the new data action I get a row not found, so I can confirm that there is no duplicate key.

If I then use API Explorer and POST a record to the table, I can then use PUT in my draft data action to update the record.

---NVM, I found it. The Request URL Template tags on the KEY for PUT but it can't be there for POST.