Hi @hawkerpl ,
I checked and found out that you are using the AJAX add to cart on your site. PPlease try to install this plugin https://www.ads-software.com/plugins/wpc-ajax-add-to-cart/ to assist ajax with our plugin.
If that doesn’t work, probably our plugin is not compatible with the Astra theme. The add to cart button on the sticky bar is disabled because our plugin could not get the product data. Unfortunately, for external conflicts like this, we cannot provide any further advice since this is a technical issue that requires in-depth inspection from the backend. However, we are prohibited to ask for that from users on this public forum due to the security and privacy policies.
Best regards.