Dear Sir, I'm a student from China. Yesterday I just got my register key. I tried to activate my mujoco but failed. I run './stimulate' in the directory '~/.mujoco/mjpro15/bin', and it ruturned MuJoCo Pro library version 1.50 ERROR: Expired activation key Press Enter to exit ... I put my license under the directory '~/.mujoco/mjpro15/bin' and I promise I've never registered the key on other OS before. My OS is Ubuntu 16.04 and I'll provide any information you need. Please help me.