Unable to change file permissions on my manuscript

I am using ver
I am trying to modify a manuscript but when I attempt to paste a paragraph into my manuscript I get a write protected content cannot be changed modifications will be accepted. When I go into the properties> security tab>permissions of the file all five permission options are ticked but appear in grey How can I solve this problem?

Can you add more details? This is the guide - How to use the Ask site? - #3 by Hrbrgr

Also, do you have a third party anti-virus?