Shop variations not showing as active in drop-down box when selected

Just recently updated WordPress and Woocommerce to latest versions. On my shop page, the default text in the variation selection boxes is “Choose an option”. When you try to select an option, the option is definitely active (as observed by inspecting code – Chrome), but the option in the variation box stays as “Choose an option” instead of showing the Active selection e.g. the chosen colour variation or size variation.

Link to shop page: https://www.themightyclothing.com.au/store

All product variation selection boxes have problems with this. Any ideas on what might be the issue?