Doesn't look like T4347 in that no errors show
stopping daemons and restarting kleoptra "sometimes" fixes it and pinentry windows shows, until it does all operations fail with pinentry missing
running pinentry-qt.exe I get
Please note that you don't have secure memory on this system
OK Pleased to meet you
We seem to have stopped it happening by randomly changing settings - generating blank conf files, reinstalling pgp4win but cannot pinpoint exactly what change fixes the error and because it's intermittent we may just be getting lucky

in I think a related scenario we are having the pinentry window not spawn at all, leading to "no pinentry" errors
Win 10 latest patches Mar 2019
Version 3.1.4-gpg4win-3.1.5
We've tried a few hacks including adding the .conf file to C:\Program Files (x86)\GnuPG\bin with
pinentry-program "C:\Program Files (x86)\Gpg4win\bin\pinentry-qt.exe"