Forum Search doesn’t work

Whether I am logged into the forum or not, if I put a search term in the ‘Search this forum’ box and click the magnifying glass, it doesn’t gives me any results. How do I use the search facility?

For example, if I go to: https://wordpress.org/support/plugin/woocommerce-gateway-stripe/

and search for signature mismatch it shows no results, but I know there is at least one thread with that search term: https://wordpress.org/support/topic/receiving-signature-mismathc-for-some-orders/

The resulting search box is: signature mismatch intext:"Plugin: WooCommerce Stripe Payment Gateway"

is this correct? I am using Chrome on a mac.