Really thank you, JWatco!
Finally I got the volume mounted using your approach. Currently I'm reindexing, because the volume appears as mounted, but the search gives me different results from old system and new one. Also, the preview is not working.
In server.conf the passphrase is in
security.passhrase=rtQAVHuVq3RejKo5ViHRsttwImTOUjyM/6B72uA+amU=
NOTICE that we miss a 'p' in passhrase
But when you copy to volumeinfo you have to write
passphrase=rtQAVHuVq3RejKo5ViHRsttwImTOUjyM/6B72uA+amU=
passphrase correctly written (with p), and removing 'security.' prefix.