Hi
I am not very experienced in network, so please be nice 
My TS-453A is connected to a 8 port switch which again is connected to my router.
I also have a Mac mini. When it is connected to the same switch I can see the NAS with Qfinder Pro, but I cannot log in. Neither through the web interface or accessing network drives. I can access the NAS nicely from other devices (eg QManager on my phone).
As soon as I unplug my Mac mini from LAN (so it only uses wifi) I can log in again. See the attached image.
What can I do? For many reasons I would like to be connected via LAN from my Mac mini. I also tried to connect it directly to one of the ports on the NAS, but that was not very successful and I spent an hour trying to understood how to setup the network switch in the NAS without success.
Info on my setup:
Mac mini M4, Tahoe 26.6.2 (although this has been a problem on previous MacOS versions)
NAS is TS-453A with QTS 5.2.10.3577 (but its been a problem for many versions)
I’m not sure what more info is needed. Here’s the screendump of network settings. The other 3 ports are disconnected.
EDIT: Just for good measures: I have of course tried with different cables and different ports on the switch. Does not seem to make a difference. And the Mac mini can access the internet through the cable and switch if I turn off wifi. Its just the connection between the NAS and the Mac that doesn’t work.