I am getting this error, as I am using mujoco210 version which is the free version released by DeepMind recently.
Missing path to your environment variable.
Current values LD_LIBRARY_PATH=/home/sagar/.mujoco/mujoco210/bin
Please add following line to .bashrc:
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/sagar/.mujoco/mujoco200/bin
Download the Mujoco version for your machine and extract its contents to ~/.mujoco directory (don't forget the dot). Now add this environment variable,
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/sagar/.mujoco/mujoco200/bin