1) Make sure you have internet connection.

2) Make sure you are using the correct host name. 

For Database:

For cs457 students: npu8.npu.edu

For cs540, and cs547: npu9.npu.edu

For Linux/Unix: 

CS230, CS385, and CS515 students use: npu1.npu.edu

For all EE courses: npu29.npu.edu

3) Connection type should be set to SSH, and the port number should be set to 22.

4) If problem still persists: contact the front desk (rm 211).