I would lift the cover if posible & look at the seal. Being a 94 the rubber seal is probably not very elastic anymore. If the rubber looks flat & molded into a squished position, I would try to find new rubber to replace it with.
As for the cleaning...........there are several medium to heavy duty cleaners on the market. Not sure which ones to try. Trail & error I would assume. Try cleaning a small inconspicous erea first incase it discolors the flooring & surrounding ereas.
Dan Sees, , 2013 Winnebago Journey 42e, 2014 Featherlite Car Hauler 3110 17.5', 2008 Mazda MX5,
2008 Toyota FJ Cruiser,2018 mercedes Benz GLA 250