I see a couple of red flaggs in your project. The layer you are trying to use Content Aware fill on appears to be about a minute long. That's an incredibly long shot for CAF to handle. The content also does not look at all like something CAF is going to be able to successfully handle.
I can't really read the error message but it could be that you have too little RAM allocated to other apps in After Effects Preferences/Memory settings. It should be at least 2 GB and 4 is better AE does not like odd numbers or decimals in the memory settings.
from the error message, I understand that AE can't save the file in the directory so maybe you have a permission problem and AE can't access the directory where you save your project, so be sure to save your project in your main hard drive or so where AE can access that directory