Are you getting an error?
A ding?
Are there any Windows or Mac excluded characters in the copied text?
Any tabs, returns, bullets, etc?
What version? What OS?
I can do it (26.3.1, Windows10) - open a file, select some text, copy it, paste it (not sure where [or why] you are pasting it), CrtlShift+S, paste... = filename with pasted text...