Please verify the model.  I don't find a 3567.  I find a 5567.

To see if this was a Windows caused problem or just coincidental, how does the keyboard keys work at startup before Windows loads?  Press F2 to enter BIOS and navigate around - don't change anything.  F12 at boot up, you can access the Diagnostics and run those and also see how the keyboard works.

Sorry for the delay.  The laptop was at my son's house. I went to settings and system and about and it shows Inspiron 15 - 3567.  It was built in 2017.  I tried what you suggested and pressed F2 at startup and changed the date and the keys are still sluggish.  Pressed F12 and the diagnostics  and no problems were detected.   

Thanks but nothing was spilled on the keyboard.  The keys are sluggish and I have to press slow and hard for the key to register.

Were the keys sluggish at startup and in BIOS?

Yes.  The keys were sluggish in BIOS.  Very puzzling.  Not sure if it is worth paying Dell to fix it as the battery no longer holds a charge and will have to be replaced.  It will probably cost as much to buy a new laptop.

I don't think Dell will fix it, if its not in some type of extended warranty,  The problem could be in the keyboard or a problem on the motherboard.  Whether a  local PC repair would touch it?  Replacement keyboards are out of stock for this model at the Dell parts source.

My Inspiron 15 Gaming 5577 is also a 2017 model.  If something happens to it, "its history" (won't be fixed).  Its not Widows 11 compatible so no use spending $$ on it.