Sorry for late reply because your topic got pending and we haven’t got any notice about it!
Please make sure you set checkout page in WooCommerce -> Settings -> Advanced like this: https://prnt.sc/AKDNU8b8OeA0
We see you don’t set a price for a product.
That’s why add to cart button doesn’t show: https://prnt.sc/ThF7UPGf5g20
Also Dokan plugin settings or extra plugin you installed can cause the issue too. https://prnt.sc/quIzUluzSG7p
The checkout page also working fine here: https://prnt.sc/R4pXhjC0B3ma
So please check the settings of your extra plugin you installed.
Hope this helps!