There can be few reason why you are seeing Unable to create checkout error in your landing page, please use the points below to troubleshoot the issue.
1) Make sure to add https before success and cancel urls while configuring checkouts.
2) Make sure that the price of the product you are adding in the landing page meets Stripe's minimum charge amount requirement. As Stripe’s processing fee combines a small fixed amount and a percentage, they enforce a minimum amount when creating a charge. Please have a look at this article to know more about minimum charge required for your currency - https://stripe.com/docs/currencies#minimum-and-maximum-charge-amounts . Kindly ensure that your products price is above the minimum charge required for your currency.
3) For Indian customers, if you registered for Stripe Indian account but you tried to sell a product with euro/dollar as currency. Please note that cross border transactions are not enabled by default, you need to provide IEC, please have a look here https://support.stripe.com/questions/requirements-for-india-export-charges . You should be able to update it here- https://dashboard.stripe.com/settings/update .