Please check the following points are this could be the reason why users are not getting linked.

First and foremost, Edwiser Bridge plugin should be configured as per the documentation.

You need to check if you have added First name and Last name in the user profile in your WordPress site.
It is mandatory to have the First name and Last name fields filled for new user account creation in Moodle. Therefore, it is mandatory to have First name and Last name fields filled in the WordPress user profile so that user account is created in Moodle when you click on Link to Moodle account button in the Users section in your WordPress site.

Check if the language code in the Edwiser general settings matches the default language code used in Moodle.

If you are using space in the first name or last name or any special characters then enable extended characters setting in Moodle. Navigate here to find the setting: Site administration > Security > Site security settings > Allow extended characters in usernames

Check if in user preferences you have selected hide email addresses by default.
Email ID is the basis on which users are registered and linked in the Moodle site. Therefore, it needs to be in show state rather than hidden.
To change this navigate here: Site administration -> Users -> Accounts -> Default user preferences -> Show mail -> Show everyone my email address should be selected by default.