iMac could not connect to NAS folder

I seems to lost access to the NAS folder AFTER running for a period of time.

On my iMac (Ventura).

Message stated "The operation can’t be completed because the original item for “Shared_01” can’t be found".

Could not connect to server " Check the server name or IP address ......."

This is temporarily resolve when I reboot the system.

I recently connected my an external USB harddisk at my router.

My router is connected to my NAS via the ethernet cable.

I wonder if this could be the cause.

I had no problem accessing both NAS and external hard drive (at the router).

But I can't access the NAS drive after period of time.

No problem accessing both on my Windows laptops at any time.

So this must be a Mac issue instead of the NAS.