Accourding to this vs-code issue
You might have had that folder open before and it now no longer exists. Can you use File > Open Folder to open a different folder in the container?
All you need to do is go to
File --> Open Folder
in the top menu
open the wanted folder and that it.
That worked for me
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…