Can't remove or add signatures on the fill and sign

I'm using fill and sign for a document. I added a signature, but want to add a different one. There is only one option for one signature, and when I try to click the "x" next to it, it doesn't do anything. I cannot change the signature nor add a new one. In the screenshot, the "x" is greyed out because I used the snipping tool, it is not greyed out when I try to click it. How do I remove this signature and add a new one? Am I really only able to have one signature stored at a time, and unable to delete it?