I have had feedback that ffp cannot longer be installed on fw 4.1+, but you are the first to report that it's automagically uninstalled.
About the package, at the moment I'm trying to download the new SDK, to see if I can find some obvious differences. Unfortunately the newest fw for my ix2-200 is 3.2, so I can't test things.
You write that you have an 'ix2'. I guess that is the ix2-ng. In that case it should be possible to downgrade using a 'recovery stick'. This will damage your data. You can use the file for the ezmedia here
. Extract the zipfile to an USB stick of at least 2GB, FAT formatted. You will have a directory emctools/hm3_images/, rename that to emctools/ix2-ng_images/. Plug the stick in the nas, and power it up with the reset button pressed. You can release the button when there is a lot of activity on the stick, or after a minute, when the stick has no led.
When everything works, the box should shutdown after 5~30 minutes (depending on the access speed of the stick).
Again: this will damage your data!