I have the following issue and struggling with that.

The "Diarium" database (size: 101 MByte) is on Synologic WebDav Server and was uploaded with Diarium 2.9.48 that was running on a MacOS Ventura 13.4 device.

The connection that was used on the MacOS Ventura 13.4 device with that it was working to copy the Diarium Database to the Synologic WebDav Server:
Server: https://<servername>.fritz.box:5006/webdav/
User: <User-Is-The-Same>
Password: <Password-Is-The-Same>

I checked and confirmed that on the Synologic WebDav Server that a "Diarium"-Folder was created and that the Diarium database was created successful!

My iOS Device (16.4.1 (a)) is using the Diarium 2.9.76 and the size of its own Diarium database is 202 MByte.
The aim is to merge this both databases!

I was struggling to find a matching configuration data to get a connection to the Diarium WebDav database from the Synologic Server on OS Device (16.4.1 (a)).

The iOS Device (16.4.1 (a)) was not able to get in connection with:
Server: https://<servername>.fritz.box:5006/webdav/
User: <User-Is-The-Same>
Password: <Password-Is-The-Same>

After some tests I found the following modified configuration with that it seems that the synchronization starts on my iOS Device (16.4.1 (a)) :
Server: <servername>.local:5005/webdav/
User: <User-Is-The-Same>
Password: <Password-Is-The-Same>

But .... after less then 3 minutes the following message on the iOS device stops the synchronization:

I tried that several times but always with the same result.

Maybe do you have some hints to solve that?
That would be great!