Ethernet connection to NAS failing

I bought the NAS recently but my transfer speeds were laughable. (10/100 router) So I bought some new kit:

TP-Link D7 Archer router (AC1750)
Cat 6a cables
Powerline (1000mps)
Gigabit switch

Accessing the NAS via wifi is much better, transfer speeds are greatly improved. I managed to copy 6.5GB in approx 2-3min. So Im happy with the wireless side of things.

However I’ve yet to successfully connect to the NAS via ethernet and cannot figure out what to do. I think it may be an IP issue but I’m stuck. My set up is as follows:

iMac1 connects via wifi and it’s all good here
iMac2 has a Cat6a ethernet cable going into a power line. The other end of the power line cable goes into a switch which is connected to the router. The NAS is connected directly to the router. I can see the NAS on my network but cannot access the files within. The messages I get are like:

‘There was a problem connecting to the server “WDMyCloudEX2” Check the server name or address’ etc

The methods I’ve tried to access the NAS include:
WD access app
Aliases on the desktop
Web portal
Cmd K and directly inputing the IP address
Opening a new finder window and clicking on the “WDMyCloudEX2” Shared volume in the side bar
Resetting the sever (on the back of the NAS)

As mentioned above I think it’s IP related but I don’t know how to resolve it, any pointers will be amazing!

(P.s apologies for originally posting this in the wrong section)

Try turning off modem/router, NAS , computer and anything else involved in this. Then restart modem/router, give it time to get up to full operation and then turn the other devices on one at a time. With all the new gear involved, an old IP address may have been stored that rebooting it all will fix if that was the issue.

I tried that and the problem persists :confused:

Any other advice tips out there?
Do I need to assign ip or something, if that’s the case then can anyone help talk me through it?