Dear friend!
According to the screenshot, the OSNR value of the device has been queried. However, he is referring to the OSNR of a path. To query the OSNR of amplified optical signals, you need to query the OSNR on the OPM8 board.

If the query still fails, see the following solution:
First, check whether the MON port is connected to the optical fiber of the wavelength scanning board.

Second, check whether the port of the wavelength scanning board is Enabled

Third, check whether the parameters are correctly set.

Thank you!