So it’s a wifi issue. It could be your Ziggo modem/router, your laptop or both.
We need some more information:
-What kind of Ziggo modem/router do you have?
-Did you ( or someone ) changed anything in the Ziggo modem/router
-Is wifi split into 2 SIDD’s for both 2,4 and 5 GHz bands and if so, to what is your laptop connected?
I'm not fond of Norton. You can try to temporary disable it, but beware what to download for a test.
The 5 GHz band is the fastest and the best to use. But not all laptops can connect to this band.
The 2,4 Ghz band is older and much slower, but ( almost ) any wifi-device can connect to it.