I wonder if someone could help.

I have a NAS in my home and I'm struggling to connect to it from any device that is connected to the mesh wifi. However if I use my homeplugs this isn't an issue.

The way I have this configured is as follows:

1) Internet comes in to a VDSL Modem and connects to a D-Link WiFi Router

2) Deco P9 is wired into the D-Link and operates in Access Point mode

3) QNAP NAS is connected to a small switch (which includes my TV, Satellite etc.) and that switch is wired directly to the D-Link router. 

I also have one of the ports connected to a set of homeplugs so I can connect it to an outdoor office. I can connect perfectly fine to the NAS from my office just not from the WiFi in the house, or if my laptop in the office connects to the WiFi also I can't see it.

Any ideas of how I can connect to the NAS from the WiFi? If I connect to the router WiFi it's not a problem but the device where I need to access the NAS currently can only connect via the mesh WiFi because of distance from the D-Link.