Thanks for your advice, but I have already done this for hundreds of products. The link to each collection appears to be broken. But seems fine in the navigation tabs. It seems to have broken overnight.
I took a look at your store theme and use the Google Chrome inspect tool and I can see that there are a quite a few errors being thrown.
Does this issue persist when viewing the store in the theme editor? If yes, please try a fresh copy of the theme file to see if it works as expected in a fresh theme file.
You may need to review the code for the collection pages if that resolves it because there appears to be quite a few broken scripts. It would probably be best to install and use a fresh copy of the theme and transfer over any unique customizations.