When a visitor switches browsers or devices Google Analytics (Universal Analytics) identifies them as a different visitor.
In order to be able to indentify logged-in visitors across browsers and devices you need to do 2 things:
- Enable the setting in Full Picture
- Go to your Google Analytics panel > “Admin” > choose the correct “Account” and “Property” with your site > choose “Tracking info” > “User ID” and swith on the option there.
Don’t worry about the code that Google will give you. It has already been properly installed by the Full Picture the moment you turned on this setting.