Using FreeRTOS in Atmel Studio 6.2
This usually happens if you omit this step from the instructions:


  And in Directories you will need to include all directories containing .h files in your project(I only managed to get working only with absolute paths). Add GCC_MEGA_AVR in Defined Symbols to tell core that we are going to use GCC for AVR microcontroller.


If you think you did that, show us a screenshot of your Directories Settings.