I found that my store has several error now. My customers should be able to choose variants on the page, but now they couldn't. The link below is one of the example. There should be M,L and XL size. It just show up with the price, but no variants are available.
Some of my products are sold out, but the add to cart button doesn't disappear. Instead, my customers are able to click add to cart button, and they will go to an error page. Please see the link below. Is the problems related to themes/ Apps? How can I solve the problems?
Thanks in advance.
@animes-pro that product has variant your theme code may be broken so I will suggest restoring origin version from the main theme copy.
From your Shopify admin, go to Online Store > Themes.
Find the theme you want to edit, and then click Actions > Edit code.
Under the Templates header, click into one of the .liquid files you have edited recently.