I had this error today. The pump (Medtronic Paradigm) offered me the option to reset - which I did, but still the error. I phoned them and they are sending a replacement ( you will need one as this is a genuine fault).
I did find a temporary workaround though. At the back end of the plunger tube there is a plastic cap. If you have the error, it will probably be protruding a little.
As you fill the pump, push it in, and hold it there while you fill your cannula. The pump sensor should then work and detect that the cannula is nearly full as it usually does, without spraying insulin everywhere, and all should work as normal thereafter.
As with any advice though - TRY THIS ENTIRELY AT YOUR OWN RISK - it worked for me - good luck!