Dears,
I'm encountering the "Network request failed" error again when syncing Joplin on my iPad to my Synology NAS hosting NextCloud 24.0.2
The WebDAV URL is https://IP/nextcloud/remote.php/dav/Notizen/Joplin.
Sync config check gives Network request failed error although user/passowrd/url is correct.
The versions I'm running are:
Synology 7.1-42661
Nextcloud 24.0.2
iPadOS 15.5
Joplin 12.8.1
Joplin on my Macbook works fine and syncs without problems.
The WebDav-Page is reachable is reachable in the browser and gives the "This is the WebDAV interface..."-response
The problem only exists since my self-signed-certificate had to be renewed which I had done using openssl via cli on my mac and importing the certificates to the ipad and my SynologyNas.
I'm a bit stuck at the moment and am not sure where to look on and continue.
Log-Screenshot:
So I managed to create a new self-signed-certificate and import it into the Diskstation. Joplin now works great again 
Most helpfull was this thread on Github: Github-Link to the rescue which I followed closely.
Only when creating the certificate using the csr I added the subjectAltName in form of an IP-Adress because I don't use a Domainname for my Diskstation in my local network.
Like mentioned from one of the commentors on github; if you use more than one DomainName you should also include them in that way.
So instead of:
openssl x509 -req -in mydomain.com.csr -CA rootCA.crt -CAkey rootCA.key -CAcreateserial -out mydomain.com.crt -days 500 -sha256
I went with:
openssl x509 -req -in IP.csr -CA rootCA.crt -CAkey rootCA.key -CAcreateserial -out IP.crt -days 500 -sha256 -extfile <(printf "subjectAltName=IP:xxx.xxx.xxx.xxx")
If you use Domainnames you will probably go with something like this:
openssl x509 -req -in test.csr -CA rootCA.crt -CAkey rootCA.key -CAcreateserial -out test.crt -days 500 -sha256 -extfile <(printf "subjectAltName=DNS:firstDNSname,DNS:secondDNSname")
That did the trick for me.
I hope this helps anyone 
