Facebook does cache the contents of the page for a long time, so the changes you make are not updated immediately. You can use the facebook debug tool https://developers.facebook.com/tools/debug/ to refresh the content.
2. Enter the donorbox donation form url and click "Debug"
3. Click on the "Scrape Again" button.
Note: If you want to share your website page which embeds the donation widget, you need to add open graph tags to your website page to display required information when shared on facebook or other social sites.