Because the operation was never about completing the save. It was about completing the moment.
: Go to Settings > Apps > FIFA 14 > Storage and Clear Cache (do not clear data unless you want to lose progress).
Try these solutions in order. Each preserves your progress if possible.
If you cannot find this, try using a third-party file manager like or ZArchiver to access the restricted data folder and ensure it isn't "Read Only". Troubleshooting Save Files