When I close a (small) encrypted DB, it first appears greyed out in “Recent Databases” in the sidebar. And if I click on it, nothing happens. But if I open it through the menu all is fine.
Opening a new window ungrays it.
DT 3.5.2
MacOS 10.15.6
I can confirm the behaviour; I don’t think that’s working as it should, no - and it isn’t described that way in the manual. As a workaround you could - if you don’t have so many databases - add your databases to the “favourites”; this works as it should - open databases are grey and cannot be clicked - once closed, they turn black and can be clicked.
Was the database currently opened? Then this is correct (as the extension is changed to .sparseimage while opened to work around the Time Machine bugs of Catalina).
No, as with the OP the database was closed and then appeared greyed out in “recent databases”, but (on my device) black and selectable in “favourites”; I actually checked with disk utility, and the database was not listed there at that time, so had been correctly closed and ejected.