Background Color Change Not Applying in Voiceflow Chatbot

I've been trying to change the background color of my Voiceflow chatbot to black using a custom CSS file hosted on GitHub. I linked this CSS file in the chatbot settings via jsDelivr CDN. Despite the correct CSS selectors (.vfrc-chat and .vfrc-chat--overlay) and important rules, the background color remains unchanged. Inspecting the element shows the CSS link but no applied styles. Could there be an issue with CSS scoping or specificity? How can I ensure my styles apply to the chatbot?