woo commerce – check out page stop working

Hi, i created a website for a friend a year ago and it has been working fine. it is on quite an old version, but nothing has been updated.

Recently for as far as we can tell for no reason the checkout page is not working. It just displays a white page saying “check out”.

The site is https://trevorjonesltd.co.uk/shop/ if you go to this item, https://trevorjonesltd.co.uk/shop/product/selmer-tuning-slide-grease-2/ add it to cart then go to check out the problem is easily replicated.

Any Help would be very much appreciated.