Continuing the discussion from Variant Product Costs not responding sometimes:
This is tremendously annoying.
I tried everything I have seen suggested: remove and add a new add to cart, etc, etc with no effect. Eventually, I found what worked is this:
Go to eCommerce and click on Products.
Select the first product and go to ‘Product Type’ dropdown - you’ll be presented with four options. Physical, Digital, Service and Advanced. Even if it says Advanced is already selected, make sure to select it again.
Repeat this for each product.
You can check that Product type has actually been selected on the overall products page - go to top right and click the PIN icon and select Product Type. ‘Advanced’ should be visible next to each product listing.
As soon as I did that, the price updates on the product page when I click on a variant button (e.g. Size, Colour, etc) and also update in the Cart.
Hope it works for you.