My store has stopped working. There is no way to select size options. The only way to get an item into the shopping cart is just as it displays by default – in the case of t-shirts that is size XS. There is also no way to select, say, a t-shirt of a different color, or a mug of a different size.
I was using the Pixelunion Handy theme, where the “options” button stopped working. But the problem also exists with Shopify’s Supply theme.
I don’t feel qualified to make adjustments to liquid code.
I should add that Pixelunion insists that the problem is not related to the theme. They thought the problem might be caused by printful. Meanwhile, printful developers assured me that the problem is not caused by printful, and suggested that I check whether the problem is caused in different theme. And in fact it IS!