Can't surf the internet anymore

Hello, everyone…i’ve been using Cloudflare DNS (both 1.1.1.1 and 1.0.0.1) which i configured directly in my router settings, for over two years, but starting last week, basically overnight, i can’t surf the internet with those above.

I contacted my ISP, wondering if there’s some kind of issue and replaced my router, but nothing…i can use my ISP’s DNS, Google and Cisco as well and they all work.
I wonder what i can do to use Cloudflare DNS again.

Here are some tech specs abt my network:

Location: Italy
Router: TP-Link Archer C7 V5 (latest firmware)
ISP: A2A Smart City (FTTH connection)

Thanks in advance to anyone that will provide useful informations.

Can you ping 1.1.1.1/1.0.0.1? Also, does this command return anything:

nslookup example.com 1.1.1.1

Seems like this could be related: