Tests

Can I reach outside ?

To use when you configured a proxy

curl https://httpbin.org/get
curl https://httpbin.org/get --header $AUTHORIZATION_HEADER

Can I reach inside ?

Start a minimalist server

cd /tmp
mkdir test-webserver &&  test-webserver
echo "fooooo" > index.html
python3 -m http.server 8081

Try to reach it on your browser

Try to reach it on your terminal

curl http://localhost:8081

You should get

fooooo

If you get Squid did not receive any data for this request., some proxy may be intercepting your request

Try disabling the proxy

curl http://localhost:8081--noproxy '*'