I migrated from a custom-built Ubuntu machine to a QNAP TS-431 and therefore archived the Time Machine
.backupbundle directory of my MacBook to a tarball and moved it to a network share on the NAS which I set up as described in the QNAP guide. However, even after successfully mounting the share, my MacBook won't backup to the new destination, failing quietly without any error message. After the "Preparing backup..." phase, the Time Machine settings dialog just states "Oldest backup: None" and "Latest backup: None".
Is it possible to get my old backup working again or is it likely to be broken?