Old quarry tiled floors like this were often laid without any form of damp proof membrane.
This in iteslf is not necessarily a problem. If the floor is well ventilated any ground moisture will often evaporate in the atmosphere.
If you cover the tiles with an impervious material such as this cushion floor vinyl the floor will start to “sweat” and become very damp.
The covering needs to be removed to allow the floor to “breathe”. Exposed quarry tiled floors can be an attractive feature of living accommodation.