Why aren't my login and registration links working?
If your login and register buttons on the widget aren't working, you probably don't have customer accounts enabled inside of Shopify.
To enable customer accounts, login to Shopify, and click "Settings", then go to "Checkout".
You'll see a section title "Customer Accounts". Make sure you have either "Accounts are optional" or "Accounts are required" selected, then click "Save".