Checkout playing relates to WooComerce functionality, so you need to be sure that it works fine with a default WC theme – Storefront. Go to Appearance > Themes > install and activate Storefront theme and test purchase again. If the problem is independent of theme, contact the support of woocommerce to get help.
Make sure that your settings for WooCommerce PayPal Checkout Gateway plugin are correct – https://docs.woocommerce.com/document/paypal-express-checkout/
We are theme support, so are able to help with issues related strictly to our theme only.