trying to add link to a subdomain

Hi,
I have a main domain – mydomain.com and three subdomains:

Subdomain1.mydomain.com
Subdomain2.mydomain.com
Subdomain3.mydomain.com

The Add Link to Facebook works fine with the main domain.

I use mydomain.com as the App Domain
I use https://subdomain1.mydomain.com/ and https://subdomain1.mydomain.com/ for the Canvas and Secure Canvas

I use https://subdomain1.mydomain.com/ as the Site URL and Mobile Site URL.

When I try to authorize the sub domain links I get an:

Facebook error: Invalid redirect_uri: Given URL is not allowed by the Application configuration.

Question – Does this plugin work with subdomains?

Question – If it does work with subdomains, how do I need to configure it?

Any help would be much appreciated!

https://www.ads-software.com/plugins/add-link-to-facebook/