If you still have your backups, could you please try if using this makes them accessible from Amanda again ?
[11:29:09] backup@openhabianpi:~$ amreindex
USAGE: amreindex [ --timestamp|-t timestamp ] [-o configoption]* <conf>
USAGE: amreindex [-o configoption]* [--exact-match] <conf> [hostname [diskname [datestamp [hostname [diskname [datestamp ... ]]]]]]
amreindex re-index Amanda dump images by reading them from storage volume(s)
Arguments:
config - The Amanda configuration name to use.
-t timestamp - The run of amdump or amflush to check. By default, check
the most recent dump; if this parameter is specified,
check the most recent dump matching the given
date or timestamp.
--exact_match - host, disk and datestamp must match exactly.
-o configoption - see the CONFIGURATION OVERRIDE section of amanda(8)
[11:29:47] backup@openhabianpi:~$