Please check the following configuration:
In Moodle;
1) Check if all the functions are added to the External Services as mentioned in the documentation.
2) Check if Rest protocol is enabled in Manage protocols.
3) Check if Token that you have generated is still present in Moodle. If you edit External services, it is recommended to delete the previous token and generate a new token.
4) Check if you have enabled 'Web Services' in advanced features.
5) Navigate to Site administration > Users > Accounts > User default preferences > Email display and check if it is set to Allow everyone to see my email address.
6) Check if Manual enrollment is enabled for all courses in your Moodle site.
7) Check if the associated user in External service is admin of your Moodle site. The token key has to be generated with the admin as the associated user.

In WordPress;
1) Check if you are using the latest Moodle access token that you have generated in Edwiser Connection settings.
2) Check if you have entered the right Moodle URL (Recommended to copy the Moodle URL from the address bar and paste it in Connection settings).
3) Check if the language code in the Edwiser general settings matches the default language code used in Moodle.

If you are using WooCommerce Integration Extension for selling Moodle courses as WooCommerce Products;
In Edwiser Courses:
1) Check if course price type is set to 'Closed'.
2) Check if you have added the optional URL ( Optional URL - It is the WooCommerce Product URL of the product that you have created for your Edwiser Course)
3) The course should be published and not a draft.

In WooCommerce Products:
1) Check if virtual and Downloadable is ticked.
2) Check if the course is associated with the Product in the WooCommerce Integration Tab.