Audacity records in stereo, playback mono

I am recording from audio tapes using a Behringer audio interface.
As I monitor the recording it is clearly in stereo, as confirmed by the green bars and waveforms. However, after I have saved the project and then play it back, it is in mono, both channels the same.
Where am I going wrong?

Here is the solution …

Thanks for your help. On that You tube video he is using an older version of Windows. The same options do not appear to be available in Windows 10.

I can’t help thinking the problem was to do with Audacity because it recorded stereo and then after I saved it it became mono.
I tried making some changes to the Windows sound settings and now it won’t even record in stereo!

Unfortunately Microsoft have moved the settings several times in Windows 10.
Try this:

  1. open the run dialog with “Windows logo + R”
  2. enter: mmsys.cpl
  3. press the OK button

Many thanks for your help.
Everything is now working fine!!