Unable to sync via Tailscale from one of two identical PCs

Operating system

Windows

Joplin version

3.6.15

Sync target

WebDAV

What issue do you have?

I have two identical notebooks (Lenovo Yoga) running Windows 10 22H2 with almost identical setup.

I managed to sync Joplin via Tailscale to my home server (Windows 10 Pro) to WebDav, using the tailscale IP and the correct port.

Doing exately the same on the similar second notebook I fail an cannot get Joplin to sync.

I know it is a bit undetailed info but as I tried a lot (including help from latest AI models), I just don't know where to look at/what to try next, as I simply don't understand what might be the difference between the two identical notebooks where one of them syncs okay?

Thanks!