Click Chip -> Compiler options and then click the restore defaults button then this should allow you to compile correctly.

If this does not fix the problem then click on Chip -> Compiler options again then you will need to put the following in to allow Flowcode to compile correctly.

Compiler Location.
C:\Program Files\Matrix Multimedia\Flowcode V4\BoostC\boostc.pic16.flowcode.exe

Compiler Parameters
-v -t PIC%p "%f.c"

Linker Location
C:\Program Files\Matrix Multimedia\Flowcode V4\BoostC\boostlink.pic.exe

Linker Parameters
-ld "C:\Program Files\Matrix Multimedia\Flowcode V4\BoostC\lib" libc.pic16.lib flowcode.pic16.lib rand.pic16.lib float.pic16.lib "%f.obj" -t PIC%p -d "%d" -p "%f"

Programmer Location
C:\Program Files\Matrix Multimedia\Flowcode V4\tools\PPP\PPPv3.exe

Programmer Parameters
-cs 2 -chip PIC%p -nogui "%f.hex"

Config Location
C:\Program Files\Matrix Multimedia\Flowcode V4\Tools\PPP\PPPv3.exe

Config Parameters
-cs 2 -chip PIC%p -config

Once you have changed all of these settings click OK and you should now be able to compile correctly.

Please note that on 64-bit systems you will have to change "C:\Program Files" to "C:\Program Files (x86)" in each of the occurrences.