Please check the steps mentioned below to debug the issue on your end:

1) Check if all functions mentioned in the documentation is added to the external services.
2) Check if you are using the Right Moodle URL which should be copy-pasted from the Address bar. It should not be an extended version of the URL e.g: It should not be used in this way. You need to use as the Moodle URL.
3) If you are using as the Moodle URL then try changing it to

Once these changes are done, try synchronizing the courses again.