Hi @zmahmood!
Thank you for sending the screenshot.
Do you know when this is happening? What actions are you taking on your site that leads to that message?
Because in this case, I think the cause of this could be your theme, your plugin, or some custom code you could have that is using these functions: session_start(), session_destroy(), or unset().
To be sure of this, please perform a conflict test by temporarily switching your theme back to Storefront, disabling all plugins except WooCommerce, and then check again if Sorry your session has expired message persists.
If that solves it, reactivate the theme first and check again. Then, reactivate your other plugins, testing after each, until you find the one causing conflict.
If you cannot perform a conflict test on your live site, we recommend creating a staging site using the WP Staging plugin.
You can find a more detailed explanation of how to do a conflict test here: https://docs.woocommerce.com/document/how-to-test-for-conflicts/.
Let us know how that goes for you!
