Custom amount – FAILURE: Invalid positive integer

Thank you for your quick response. I’ve looked at the documentation but the same error occurs even with the shortcode provided in the documentation example:

Shortcode:
[accept_stripe_payment price=”0″ name=”Test donation for a good cause” button_text=”Donate Custom Amount”]

From the debug log:
[04/25/2018 9:14 PM] – Payment processing started.
[04/25/2018 9:14 PM] – Triggering hook for addons to process posted data if needed.
[04/25/2018 9:14 PM] – Checking received data.
[04/25/2018 9:14 PM] – Checking price consistency.
[04/25/2018 9:14 PM] – Getting API keys and trying to create a charge.
[04/25/2018 9:14 PM] – Firing pre-payment hook.
[04/25/2018 9:14 PM] – Processing payment.
[04/25/2018 9:14 PM] – FAILURE: Invalid positive integer

However, the normal shortcode buttons with fixed amounts where price=”XX” seem to work.