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.
It is because of this RIC <FF192000900.U>. If I removed this RIC, the data can be retrieved properly.
I also got the error when using Eikon Excel. It returned "Unable to collect data for all requested fields." Because the problem also happens with Eikon Excel, you can contact the Eikon support team to verify the problem.