Not seeing backup in list, to continue incremental

I've created an encrypted incremental backup on an external drive (incremental scheme 1/5, ~12 hours), but coming back a week later:

- I can see the TIB file in windows FileExplorer and double clicking on it prompts for password and lets me browse ok.
- but Acronis2015 doesn't list it by default. +AddBackup lets me browse to the external drive, then prompts for the password, then .. nothing changes - still not listed anywhere to continue the incremental backup.

This worked in the trial and older versions.
So now I've paid and found my support ran out before I ever knew I'd need it.