Hey Natasha,
Thank you for reaching out to us!
I’m so sorry to hear that you are having problems with your checkout page. Let me help you to solve this!
To get started, I would recommend you to make sure that all of your plugins are up-to-date.
After that (if the issue persists after the upgrade), please enable WP_DEBUG and WP_DEBUG_LOG and share with us any messages you see while accessing your checkout page.
All WP_DEBUG messages will be stored in a debug.log file in /wp-content.
Thanks!
Patricia