I would suggest you use task manager to shut down all instances of cmd.exe. It should be showing in Applications, but something may be out of alignment.
Do a cold boot, which mean shutting down your system and restarting.
Look for the Command Prompt on the start menu, right click and select properties. Select the shortcut tab and see what it shows for a Run option. Is it Normal Window, or something else?
But anytime something does not work as it is designed, I recommend running the SFC /scannow command. Since you cannot get into the Command Prompt window, this may not be available. Perhaps it might work in Safe Mode.
f you cannot get into a Command Prompt Window, I might suspect a virus could be causing a problem. Malwarebytes seems to be a fairly good anti-virus for scanning your system if whatever you already have has not found anything.