Synology security certificates

Hi all,
I have a small (home user) Synology NAS. I can access the drive remotely through security certificates provided by Synology. That bit is 'fine'.
One important use for the NAS is backup - for this I use a product called 'Active Backup For Business' - this has client software that sits on my PC and communicates an incremental backup to the NAS on a schedule. This DID work GREAT but has stopped. I think that it is not possible for me to access my NAS over https over the local network (192.168.x.x). I think I need to create and install a security certificate to allow me to do this.
The NAS has a fairly simple way to create security certificates but I don't know what I'm doing and think I'm in a muddle.
I'd like to learn a bit more about it and wondered if there was someone who might run a remote access session with me (eg Teamviewer) to talk me through this problem and fix it with me?