If that is unhitched, what weight have you got at the hitch?
ETA. A bit of digging on the net produces this.
Understanding all about tow ball height… | Caravan Chronicles
If the car towball is at the correct legal height & the new trailer hitch height with the trailer level is outside the spec given for use with your vehicle then seems to me that the trailer doesn't comply with regs for use with your vehicle type - and is therefore not suitable for use with your car - & I would say that is an issue for the seller to address.
BUT the EU reg does mention offroad vehicles & it seems there may be an exemption for them in respect of hitch heights & that could explain the height of the hitch on this trailer. I.E suitable for use with 4x4s but not others.
Which would appear to be a Sale of Goods Act issue as not fit for purpose - you've told the seller what your towcar is & you've been sold an item that doesn't fit your tow car.
If they won't play then you may have to reach for a solicitor, but where you'd find one that understands this could be another matter!
CAVEAT. I could be talking utter tosh so best check!