Ecu damaged

Hi my name is cleophas.on the 02/12/24 I brought a Audi q5 2.0 tfsi ecu to check what is wrong,n when I received my ecu back the ecu doesn’t crank the car anymore and I took it back they say to me I mst throw away bt I gave them my ecu working all it did was crank the car now the car don’t crank plz advise,do I open a case agains ecu xpress or do I take matters in to our own hands