When I open a newly recorded aup file "Error opening"

When I open a new .aup file of my carol concert I get an error message that says:
“Carols 2015.aup is already open in another window” How should I proceed?
I am using Windows 8.1 and my Audacity is version 2.1.0. The .aup and backup.aup files will not bring up the recorded waveform when I use “Recent files” or Open. The waveform was perfect when I recorded the 1 hour concert and I saved the aup file and also a backup file using Save Project and save project as…buttons.
Mike Crouch

Is it already open in another window?
Have you tried closing down Audacity completely and rebooting your computer?

What do those commands do, assuming the project is not already open in Audacity?