It looks like that space has a base project set, and that base project is a copy of another project. Our system doesn't currently support this behavior, and we recently made a change in RStudio Cloud to prevent spaces from getting into this state. I'm guessing this base project was set before that change went live. Sorry about that!
To create projects in this space, the base project setting will need to be updated. Are you an admin of this space? If so, you can either select a different project to use or clear the current selection in the space's settings, and you should be able to create projects again. You can see more info (+ screenshots) about how to do this in the Guide.