Unable to Stage All and Commit new changes.

[3Dlunatic]

I've been using SourceTree and git for version control of my Unity game project. Recently I haven't been able to [Stage All] or [Commit] my new changes. I don't understand why. I don't know if it's possible to attach a screenshot here, so I can only describe what I see.

I have some [Unstaged] files, and on the right side they have a [+] sign. The [Stage All] button is grayed out. When I select the files manually and click [Stage Selected], I get notifications in the right window saying "No changes in this file have been detected, or it is a binary file."

I have made changes to my project, and the [Commit] button on the top ribbon shows there are uncommitted files. But I am stuck at this point. Any help is appreciated.