I am really not having much luck with Diarium on Windows...
I'm not blaming Diarium, it's Apple's fault - they make is so difficult to do things on everything and have a ton of compatibility issues unless its an Apple Device. (No, Apple I'm not buying a Mac!)
First there was The browser update issue with the security keys not being supported and also the incompatibility due to Advanced Data Protection issue.
Yesterday, I tried to setup WebDAV on my NAS only to find that after the last update they (The NAS manufacturer) removed that feature! That was my last hope of getting around all the extra security issues I was faced with in trying to sync with iCloud from Windows. I now only use Diarium on my iPhone as It can not and will not sync.
I guess I'll have to wait for the update when it arrives where we will be able to lock our diary using our own password, for now, Diarium on Windows is redundant for me. 🙁