Kindly perform this check to see if all the required domains are white listed for the smooth functioning of Quizizz. The result of the check should have green check marks next to each of these tests as shown in the image.
However,If you see anything other than green check marks next to each of these tests, then please contact your school's IT staff and share this page with them (https://quizizz.com/check). They will need to change your browser/firewall settings to allow Quizizz to work.
To know which domains need to be whitelisted on the firewall, please refer this link.