When connecting the switch, the Internet is cut off in the router, what should I do?

Question

Computer networks

Help, I don't know where to dig anymore.
In general, the situation is as follows. The network architecture is as follows:
1. The cable with the Internet is included in the router.
2. from the router there is a cable to the switch.
3. from the switch cables to other PCs (2 pieces)
The second time the following happens. When you connect the switch, the Internet is cut off in the router, even Wi-Fi does not work.
happens it to the second switch already. and after buying a couple of weeks the second worked fine. then the network began to fall off.
Beeline technical support refers to a broken switch (but that two switches can break in one node - I believe weakly. Especially since now it’s a pretty high-quality model from netgir. Tell me
where to dig here?

Answer 1

Enable logs on the router. And show)
Do not stick a wire from a working switch into a working router. Not everyone digests it.

Answer 2

Plug one of the PCs directly into the router connector where you plug the switch and look.
If everything works - the problem is in the switch, if not - the problem is in the router.