Try to sync to GitHub, but the commit changes button is grey out!

As you can see in the screen below, AI Studio already detected a file change, but the “Stage and commmit all changes” button remain grey out! I can’t sync the code to GitHub.

What’s might be wrong? It was fine all morning!

After few hours, I found out the button is back to normal again and I can’t click “submit commit” again. However, what’s the mechanism which stop it from working? I’d like to know.
BTW, quota is not exceeded, since I don’t see any warning on AI Studio user interface.

Let me know, if you have a clue.