I use the function eikon.get_data() from Eikon Python API to retrieve option data. The fields I use are 'TR.OPWAskImpliedVolatility' and 'TR.OPWBidImpliedVolatility'. Sometimes I got empty data while I am able to see the numbers in the DIB window in Eikon API. For example, I can see the values of these two fields for the Ford Motors options by clicking on the fields in Eikon DIB, while the Python API is returning empty data.