I'm unable to insert my email templates

I'm unable to insert my email templates

A day ago it was working to click the "Insert HTML" button to load my email templates. Today when I was trying to insert my email template via the "insert HTM" button when I click the "insert" button after the template doesn't load and it says, "[object HTMLBodyElement]". Why isn't it showing my email template as it did before. Someone please help me as this is urgent I need these emails to work for communicating with my customers. Thanks in advance.