Hi, I set up back in stock flow for my Shopify store owner. I have updated Shopify theme.liquid with the klaviyo provided sniped code installation. But in product page not showing "notify me when available" button. only shows "SOLD OUT"

And my client Shopify theme is "Dev working z dzine Niket[6/6]"
What is the reason for not showing "notify me when available" button, Have I missed anything? Or what to do more.
Please help me with a solution. I will be greatful to you all.
Thanks in Advance
A.Hossain