I did what you advised and both devices showed 6 different numbers. So there has to be an issue with the 16 digit secret key.
The 6 digit codes were different from each device. Both in synch. I'm just not sure what to do now.
Did you compare the generated codes on both devices at the same time? The generated codes are temporary and change every 30 seconds or so. If you get different codes then one or both your devices are out of sync (assuming you you imported the correct secret key).
Since those codes are temporary, you have to enter the generated code on bittrex, or whatever service you want to access, before it expires or it will become invalid.