I recently encountered an issue on my machine where copy and paste functionality ceased completely or acted erratically. Sometimes it would work, other times it wouldn’t. I do a lot of this, so I was pretty annoyed. I have another machine without this issue and the main difference between the two was the anti-virus program I run.
I did a little searching and the issue ended up being Webroot’s Identity Protection
Quickest way to enable cut and paste again is to set Webroot to ‘allow’ the applications. I don’t see a lot of need to ‘deny’ an application, but that will be up to you.
To get to the settings, click on the gear next to Identity Protection
Then search the list for any item that may have Deny enabled and change it to Allow or Protect.
Link to the issue – https://community.webroot.com/t5/Webroot-SecureAnywhere-Complete/Copy-Paste-Stops-Working-in-some-applications/td-p/21588