Deprecated: is_ajax is deprecated since version 6.1.0! Use wp_doing_ajax instead. in /home/xxxxx/public_html/wp-includes/functions.php on line 5211
To solve this, go https://developer.woocommerce.com/releases/ and download and old version of Woocommerce, e.g 5.9.0 Zip file and then uninstall new version of woocommerce plugin which is 6.1.0 and install 5.9.0. The error will go.
If you want to use new version of woocommerce, wait until new version of 6.2 available or delete entire site (Make backup first Site and Database) and start new site copied on old site. Another way is updating WordPress