I have a free membership. Is there a reason I can't save and/or edit the forms that I'm creating?

You should be able to save and edit forms without any issues. 

Can you please provide us more details about your issue? Which form are you unable to edit? Also what are you trying to edit on your form. If possible please provide us a screenshot of your issue. 

In case that wrong version of your form was saved you can revert your form to previous version. 

How to view form revision history

Also please do not open your Form Builder in multiple tabs or browsers, because this way wrong version of the form is saved. 

Looking forward to your reply.