A spectrophotometer connection does not share well between applications. If the spectrophotometer has already been calibrated or used in one application, subsequently opening another application and attempting to connect to the spectrophotometer will result in an error. Applications that could use the spectrophotometer include Color Engine Pilot, Verification and the Linearization Tool. Third party software such as X-Rite's Measure Tool can also cause the problem.
Esko Verification will show a "failed to connect to device error" when trying to calibrate.
Clicking the Measure button in the Linearization Tool will result in a message of "Open failed".
Color Engine Pilot will show "Calibration error: Exception in I1_SetOption: Invalid device handle".
Close all the applications that could be using the spectrophotometer connection. Start the needed application and make sure it is possible to calibrate.