Looking at the styles, those 2 input boxes are getting a font-size of 0px from your template. When I set a different size in my browser dev tools, I was able to see the text entered. You can add the following to your SCLogin theme to make a valid size font:
input#sclogin-username.input-block-level, input#sclogin-passwd.input-block-level {
font-size: 14px;
}
I'd suggest making your own theme for SCLogin, so you don't lose any changes if you upgrade our modules. You can find
instructions here
Hope this helps
-Melissa
Impossible to add something in login form
