Yes, WHMCS Bridge is compatible with WordPress Multilingual (WPML). Please make sure you follow the below steps:

1. Please install the WPML plugin first by following their instructions (see http://wpml.org).
2. Go to your Pages section in your WordPress admin and Edit your WHMCS Bridge page (the one created by the plugin).
3. On the edit screen of your WHMCS bridge page, add a new custom field called cc_whmcs_bridge_page and set its value to WHMCS

** NOTE: If you are not seeing "Custom Fields" on your Edit page, click on the "Screen Options" tab at the top right of the edit screen and tick "Custom Fields"

4. Save your changes.
5. While still on your edit page, under the "Multilingual Content Setup" section, make sure that the custom fields are set to "Copy", particularly the cc_whmcs_bridge_page field you have just added. 


6. Click on "Apply" under the "Multilingual Content Setup" section.
7. Go back to the Admin -> Pages section (to list your WordPress pages), next to your Bridge page you will see a "+" icon below your additional language flag, click on the "+" icon. 
8. Give your new language bridge page a title - make sure the slug is the same as your WHMCS bridge page slug to avoid any issues. 

** NOTE: If you can't change the slug to the same as your existing bridge page, return to the page list and use the "Quick Edit" function to change the slug to be the same.

9. Publish the page.

You will now be able to use the WPML language bar on your website to switch languages of your WHMCS bridge.