Laying underlay on concrete floor

Might be worth telling them now just so there's a problem "on the record" but that smell's normal and can easily take 4-5 days to go, in extreme cases even a couple of weeks. Great info here: https://blog.fantasticservices.com/how-to-remove-or-reduce-new-carpet-smell-tips/

Ensuring you keep the underlay straight and gap-free, staple it along its edges inside the gripper. Use adhesive if you are laying carpet onto a concrete floor. Use tape to stick along the full length of joins. Use the knife to trim off any excess underlay inside the grippers.

Underlay needs replacing if smells or floor underneath is damp.

You only glue all underlay to the floor when durafitting which means your also sticking the carpet to the underlay,that is only done when customer requests for this or you have no way of fixing gripes but there's normally always a way,most durafitting is done in hotels ,where there trolleys being pushed along floor,or big areas like bingo halls.ect....the cat smell sounds like you have a damp issue so dpm,,,damp proof membrane could be a solution.any damp reading over 200 would need this

The underlay may have been wet or if bad quality hence the smell

We have fitted many carpets over concrete, the glue shouldn’t cause such smell

Hold back it's more likely the adhesive could have been solvent based which has a smell like ammonia!!!!!!!! Which will evaporate in due cause I've had a similar situation myself ,also if the underlay was a rubber construction and wrapped in a plastic bag as is normal that can sweat and cause an Oder !!!!

If it was rubber underlay it is normal for it to have this smell, it goes away after a week or two

Removal will be hard work if underlay stuck down just pull the carpet back and take a look your self

The underlay needs to be glued to concrete floor as staples will not work