There’s a lot of stuff that Norton and McAfee don’t catch, because they mainly look for viruses. So, if you accidentally installed some software that loads you up with spam or something, they might not even look for that. Try this, the free version is very good at finding bad stuff like that:
https://www.malwarebytes.org/mwb-download/
Just be careful because they try to trick you into enabling the “free trial” of the premium version if you install the free version. That one will expire in 30 days so just decline that.
Norton (Symantec) and McAfee are terrible products that catch very little. I get to clean up after them enough.