Can't sign document

Hello, I have de Adobe Acrobat Reader DC - Português (21.005.20048) version on Windows 10. 

When I try com sign an interative document, the Sign botton doesn't work.

I click on the interative rectangle to select the signature I want. Done.

Select the signature and pattren. Done.

When trying to click the "Sign" botton to conclue the process, It doesn't work, like it isn't activated.

Could you help me?