I installed an Arduino Due board from the boards manager without any problem and successfully uploaded my sketch to the board.
I turned off my PC and the next day I came and saw that there is no "Due" option in the boards menu. I have come across this problem many times and I don't know what causes this. Every few days I have to re-install the board. My IDE is 1.6.13 and I also tried 1.8. My OS is Windows 8 with full administration access. I have also installed third-party boards such as NodeMCU without such a problem. Any Ideas?