A Queue is not updating a ticket via email

Greetings,

I have a single queue that will not update a ticket via email, but will only
create a new TT if the original ticket is responded to.

I’ve poked around the system to see if I could find anything, and I came up
with nothing. Are there any known issues where an email response to a
specific ticket will only result in a new ticket being opened?

Thanks,

David Bauman