Why can't I upload games? It doesn't exceed 1GB.

Because there are limits, as explained in the Creator FAQ. Please follow the instructions there.

Is this different than the last post you made about it here ?

You mentioned you uploaded your project then. If you are receiving the same error, there’s a chance your internet connection is a bit unstable at times, or Itch.io might be temporarily having an issue. I’d suggest to try again later.