Hi there,
INTERNAL SERVER ERROR (or usually 500 error) are most often caused by conflicts with code in another active plugin or the theme.
To check for conflicts, please temporarily switch your theme back to the default Storefront theme and disable all plugins except for WooCommerce and PayPal Checkout, then check to see if the issue is fixed. If it is, then switch your theme back and reactivate plugins one-by-one until you find the one that is causing the issue.
You can read about testing for conflicts in our documentation here:
https://docs.woocommerce.com/document/how-to-test-for-conflicts/
There’s also a guide for troubleshooting “500 Internal Server error” here:
https://www.wpbeginner.com/wp-tutorials/how-to-fix-the-internal-server-error-in-wordpress/
If you are still having issues, please check under **WooCommerce > Status > Logs**, and see if there are any entries in the dropdown for “fatal-errors”.
Also, please enable debug logging under **WooCommerce > Settings > Payments > PayPal Checkout**, then try another test order to generate logs. After that, check under **WooCommerce > Status > Logs** again for an entry in the dropdown that mentions ppec (PayPal Express Checkout) and provide the logs here.
I hope that helps!
