/wp-content/plugins/order-signature-for-woocommerce/swph-woo-order-signature-light.php on line 70
This error will likely occur after upgrading your version of PHP to 8, WordPress to version 6, and/or the WooCommerce plugin. To fix this error navigate to the file with your SFTP client and replace (is_checkout) with (is_checkout()) on lines 70 and 89.
This will resolve the error.