As soon as I put in a “data-client-token”, the PayPal button refuses draw. Any idea why?

In my page I have

<script src="https://www.paypal.com/sdk/js?client-id=REDACTED&enable-funding=venmo&currency=AUD" data-sdk-integration-source="button-factory"></script>

As soon as I put in a data-client-token, e.g.

<script src="https://www.paypal.com/sdk/js?client-id=REDACTED&enable-funding=venmo&currency=AUD" data-client-token="DEPOSIT" data-sdk-integration-source="button-factory"></script>

the button refuses to draw. Any clues as to why? According to the documentation, this additional markup is permitted.