Time Machine/Migration Assistant says "No Volumes"
My machine recently needed its motherboard replaced as the GPU died on it. When the tech rebuilt the machine they wiped the drive - which is fine, as I have time machine backups. But when I try and restore backups now via Recovery or Migration Assistant I get a "no volumes found" for my iMac. The version of macOS is the same (Catalina). When I browse the Time Machine I can see the sparsebundle and it's 2.1 TB so there is definitely something there.
How can I get my files back? Thanks.
iMac 27″, macOS 10.15