edited on 08-07-2019 10:38
For situations like this, I highly recommend using the UPC Wii-Free networks as a test.
This is activated for everyone by default. Get/set your passowrd for it and then test it. You can't test it on your own Connect Box (or Horizon box for those who like an s&m version of a cable TV box) so you need to *turn your modem off* and then you should hopefully see the UPC Wi-Free network being transmitted by one or more of your neighbours. Connect to it. Log in and surf, to prove it works. Then, turn your box back on and use your own network as usual (as the free network is limited in speed).
In future, if you lose internet, do the above. If you can log in and surf, it means the issue is with your cables/box. If the login fails (it'll connect but reject your user/password) then it means the neighbour's internet is down too.
I always do the above when I lose internet, as it's comforting to prove the issue isn't just me