Alexander Shofner-Geidt wrote:

Windows 10 Home, 64-bit, all current updates. Seems to be working fine.

You know how F5 is supposed to put a time/datestamp on Notepad and/or Wordpad
when they are open and in focus? This works on all my other computers,
currently Windows 10 Pro and Windows XP. It worked all the way back to Win9x.

On the brand new Dell it does not work. The Dell tech support (warranty)
doesn't know. Google searches are baffling and confounding...

Is the Fn key perhaps stuck down? Have you tried prying it up, like
with a fingernail emery board (flexible but stiff enough to lift a key)?
What does the blue legend of the F5 key says it does?

If you turn over the keyboard and tap the laptop to shake out the filth
behind the keyboard keys, does a lot of debris fall out? Been feeding
the keyboard any soda in the past?