Do you have another anti-virus or firewall program installed Monica? .....
Go into Control Panel, Windows Security and check to see if another program or programs are running. Windows Security will tell you which program(s) are active if you pull-down each window and read the information.
If Windows Defender, Windows Firewall or a Norton program is running you'll have to shut them off and uninstall the programs that you are no longer using.
You can deactivate Windows Defender without removing it from your computer.
Elliot