When trying to connect your YouTube to your page, you might be using the wrong Youtube channel link.
You need to use your full channel link - not the shortened version. You can find your full channel link by going to YouTube Studio.
To find your channel's URL:
1. Sign in to YouTube Studio.
2. From the left menu, select Customisation. Basic info.
3. Under Channel URL, you can view and copy your Channel URL.
or, use this website:
Enter any of your YouTube channel links, it will give you your full channel link.