It looks like your browser settings may have disabled "Third Party Cookies". Hatchlings needs this setting enabled to connect with your Facebook account.
What is a third party cookie?
Third party cookies are a browser feature that allows websites to share specific data about you between each other.
Why do you need 3rd party cookies?
In order for Facebook login to work with Hatchlings to allow you to connect to your account, the Facebook libraries we include on our site must be able to access the cookies set by the Facebook site when you login. Third party cookies are how Facebook determines who you are so they can grant our code access to your Facebook details like your basket ID, name, and friends list.
Why is this disabled on my browser?
It has always been possible to disable this setting on your own. But if you didn't purposely change it, the setting may have been flipped in a recent update to your web browser.
Recently, some browsers such as Google Chrome have been switching this setting automatically. Disabling third party cookies can have some privacy benefits but it also causes issues with many websites which require this feature to run. Hatchlings (and any site needing to connect with your Facebook account using their libraries) is one of the sites that needs 3rd party cookies enabled.
How do I re-enable 3rd party cookies?
Find "Block third-party cookies" in your browser settings and ensure that it is disabled.
If you are using Google Chrome, go to Settings > Content Settings > Cookies by pasting chrome://settings/content/cookies into your URL navigator (where you type in websites), and turn off "Block third-party cookies".
I use a browser other than Chrome