AppCenter does not open

Can you please open a Terminal and enter the following command:

killall -9 gnome-software; gnome-software --verbose 2>&1 | tee ~/gnome-software.txt

This will first kill eventually running App Center instances and then try to run it with verbose output of what is currently happening. Can you then please upload the file “gnome-software.txt” which has been generated in your Home directory for further analysis.