Product Block Not Adding Items When Selected

I’m having an issue with the Product Block that I’ve never experienced before. When I click the ‘Browse for Products’ button our product catalogue opens like normal, however when I select a product and click ‘Add Products’ nothing happens. The catalogue window closes but the product hasn’t been added to the block.

I thought it might be an issue with the product being brand new, but I’ve tried adding older products with no luck. I’ve also tried opening an old template and adding new products to its block, and I’m having the same issue. I can remove an item that had been selected previously, but it won’t add the product back once deleted.

We’ve been using Klaviyo for many years and never had this issue before. Is this something anyone else has dealt with? Or should I just reach out to Klaviyo support?