PNG signature not showing up in a reply email

So I am having this weird issue.  I created a signature which is just a png file, no text.  It will show up fine when I compose a new email but when replying to an email it won't show up at all.  I have tried to manually insert it from the drop down and it just creates a blank return in the body of the email.  I have tried creating another signature that is just text and no png file and it actually will auto show up on a reply email just fine.  What's going on with my signature??  I have used outlook in the past and had similar signatures that were just a jpeg and it totally worked on replying to emails.  Is it because I am using a png?  Very confusing.