Did you set up an Adobe Creative Cloud account when you downloaded Lightroom? You need this account even if you are using a free trial version. When prompted for username and password use your Adobe account information, not your Mac ID.
You can visit Adobe Customer Care for help and to live chat with customer service. You will need to sign in with your Adobe account information to use this to https://helpx.adobe.com/contact.html.
You may receive emails from this board if your preferences are set for that. There is a checkbox “email me when someone replies” when you post something, but if your account settings are set up to not receive emails, you won’t receive any even with this on. Click on your profile pic in the upper right corner to check your account settings.