From the Main Menu go to the starfire receiver, on the top of the screen go into the settings button, then part way down on the left side of the screen there is a 8 digit Differential Correction Frequency number, that number should be 1545.9675, if it is something other than that you will need to change it, if it is greyed out there is a Default check box beside the frequency number, uncheck it and then you can press on the box with the number and it will open a numeric key pad, enter in the number I specified and accept it, do not recheck the default box as it will change back to the wrong number, then when you can do it get the software updated in the receiver. 

Another thing it could be is that you are not on the proper RTK base station and the SF2 fallback is expired.