MasterCraft Roofing

MasterCraft put a new roof on our house back in May . However, we noticed that it was leaking soon after. They had to tear off the roof because the shingles were torn from nails being shot through them. The back of our house has a flat roof and they used a pool liner instead of tar. They have come out twice to repair the flat roof, but it has ruined our ceiling because it's leaking through the bathroom fan. The last time they came out was in July 2022. We called them before Hurricane *** to let them know that it was leaking again in the same location. I have called them three times since then and the new owner is taking over shortly. She told us she would talk to the previous owner to see if the 10-year warranty would be honored. I don't think a new owner can void out the roof warranty. Please help or advise me.