Library file not recognised for repair/rebuild

[jss366]

Hi
I have a library file (database) of all my references, haven't used Bookends for a while, and the file has been up to cloud - Google drive - and back again to my mac.
Now I try to open the library file it is grey and not recognised by Bookends, to repair, rebuild or whatever. It seems to be missing a file extension (suffix), should it have one? If so, what?
Thanks!
I did search the forum for this question and found no reference to file format or suffix etc.

[Jon]

It's

.bdb

Jon
Sonny Software