You found it, you cleaned it up, you used something that smelled strongly of lemon, and the carpet looked fine. Then they went back to the same spot. To you the problem was solved. To them the marker was still there.

A dog or a cat has a nose good enough to detect what is left after your clean, and what is left is the part that soaked in. Urine goes through the carpet, through the backing and into the underlay, and a surface wipe removes the visible ten percent. The rest dries into crystals that reactivate with humidity, which is why an old spot smells stronger on a wet day. Masking it with fragrance does nothing to the source, and it teaches the animal that this is where the toilet is.

An enzymatic cleaner is a different mechanism entirely. It carries enzymes and bacteria that digest the uric acid and the proteins, so the compound producing the smell is consumed rather than covered. That takes time, and it takes contact, which is why the instruction is to soak rather than to spray lightly. If it did not get as deep as the urine did, it cannot work on what is down there.

So over-apply, cover it, and leave it. Ten hours is not too long.

Here is the limit. Enzymes are living and fragile. Cleaning the spot first with anything else, especially a steam cleaner or a strong disinfectant, can kill them or set the stain permanently with heat, and then this fails through no fault of the bottle. Use it first, not last.

It is also slower on an old stain than people expect, and often needs a second application. Set-in crystals took months to form.

And it does not fix why it happened. Repeated indoor accidents in a house-trained animal are a health signal or an anxiety signal, and no cleaner addresses either.