if it really is varnished, then the finish will not easily be damaged, so I'd start by stripping the surface clean. It might be that is has an incompatible polish on it.
try rubbing a small test area with a rag moistened with dilute flash or other GP cleaner in water, and rub dry. If it dries clean, then clean off the rest.
if the surface feels soft after cleaning, something has atacked the varnish. Sometimes it will harden up after it dries. I don't know what to do about that, short of sanding off and revarnishing.
If your attempts at cleaning strip off the finish and you go back to bare wood, it was probably an oiled or waxed surface, and you can re-oil or re-wax, but you will probably need to clean off the incompatible polish. It might for example be a silicone polish applied over hardwax. Some floor clean-and-polish treatments leave a film that builds up over time, and has to be periodically stripped off. I'm thinking of Johnson's Kleer, if it is sold here, instructions s/b on the bottle.
You do need to work out if it is a laminate or a hardwood floor. Look at the edge of the boards in a doorway, where they will have been hidden under a cover strip.