There is a new bug with Safari on OSX El Capitan that is preventing piZap from saving to computer for all flash based photo editors. Even worse, it can crash safari. Apple is aware of the bug and it will be fixed in an upcoming release of OSX, however we don't know when that will be.
The only current fix is to use Google Chrome or Firefox to access piZap. We are sorry for the inconvenience but this one is our of our hands.
The piZap Team