So it sounds like the thing you are calling “network switch” is acting as a router and a DHCP server.
With the NAS on the switch; and the laptop on Wifi; you essentially have a “double-nat” setup; which can cause funky problems depending on the router firmwares.
While you are on the same network; the devices are on different subnets in a double NAT setup.
This is not really a bad thing; I have run this way in the past: I wind up in this situation when I am dialed into my network with VPN.
One thing I have noticed in this mode is that the access via “device name” doesn’t work reliably. I tend to always refer to the NAS by ip address (either in a browser to get the dashboard; or file explorer to access files)
Give this a whorl and let us know.
(PS: OS3 is working with SMB1 - - > when you use file manager; the network section will NOT show the NAS in a double-nat setup; but you can still access using the IP address)
Or, your “main network router” is the DHCP server and the “wifi router” is causing the double NAT. Either way, try plugging the main network router into the wifi router’s WAN socket and turn off DHCP in the wifi router (or select “Access Point” mode instead of “Router Mode” in the wifi router).