[tomsem]

What about your Latin dictionary? If you go to Settings, Language & Dictionaries, Dictionaries, where does it show up? Is it under Latin, or under English?

The one I have (‘A Digital Latin Dictionary’ by Thomas McCarthy, from Kindle Store) registers as a dictionary for English (‘English-in, English-out’), so it appears as one of choices for the default English dictionary.

I think the use case for this dictionary is to translate Latin words that occur in otherwise English text into English. With older Kindles (at least through Kindle Touch), you could not switch dictionaries without going to Settings, where you could choose Default dictionary of those available for a given language. And to use the Latin dictionary, you would need to go to Settings and make it the default dictionary for English (meaning you could no longer look up English words without switching the Default). Not very convenient.

On newer Kindles there is flexibility to choose any dictionary for any book while you are reading it (as you have been doing), as well as set a default dictionary for each language for which you have more than one dictionary. But this Latin dictionary has not changed, it still cannot be set as default for Latin because it still says it is English-in.

It should be possible to use the calibre metadata editor to change this Latin dictionary and mark it as ‘Latin-in, English-out’ so that it would become automatic default for books marked as Latin (on newer Kindles you could still select it to translate Latin found in other books). I haven’t tried it, but then, I don’t have any Latin books so there would be no benefit to doing so (I can use it as needed without any issue).

If your dictionary is marked ‘Latin-in, English-out’ (as you would expect for most translation dictionaries), then I don’t know what the issue could be.