Updating an account UDF with current date-time

I have a UDF of date type, and I want to update it with the timestamp of the last received backup report email.

I’ve created a step using Autotask - Direct API Calls, and I’m attempting to update the UDF with the current date/time using:

{{date add=“0 seconds” subtract=“0 seconds” to_format=“dd-mm-yyyy” from_tz=“UTC” to_tz=“UTC”}}

This does nothing - the log shows it updating the UDF with ‘null’.

What am I doing wrong?