Why can't I add the 1 year variant to my cart?

This is my product URL https://halloweencontactlenses.com.au/products/22mm-full-eye-black-sclera and if you can check there is a variant with the name 1 year. I can’t add 1 year variant in cart and it’s happening for all products. I tried chatting with support but they seem helpless in this issue and asking me to revert to previous version of theme.

Hello @adityachauhan

I see your adding cart feature so i suggest please check the code snippet where you added products via code because there invalid parater error (422) showing on page.
See below image for reference