Is the default gateway not available on the local network?

Question

Computer networks

There is a local network, there is a host computer, 10 more PCs (Win10) are connected to it via the network, the last time they were turned on in the spring of 2017, and the network then worked fine and there was access to shared folders.
Well, the other day the computers were turned on again, and 6 PCs showed problems with the network, and all the PCs that are connected to the Internet began to download updates.
I want to note that these 6 PCs are connected to a separate hub, and those 4 PCs to another.
I still rummage a little in networks (or not rummage), but I need to fix the problem.
I ask for your help gentlemen)

Answer 1

The easiest way that does not require knowledge of the network is to switch one of the 4 PCs to the second hub and see if the network appears. if appeared - the problem is in the gland.
plus the standard Windows network troubleshooter will tell you what the problem is - no DNS, no network at all, and so on.