A bigger/more complete screenshot would make it easier, but on first glance, it looks like your access to the site is blocked. In that case, you need to contact the site owner to determine why
Thanks. What’s interesting is the link to site works. The preview of the site is giving this Attention Required message (Google Classroom always gives a preview of the site when you post a link to an assignment). We are just worried that students won’t click on it due to the preview, but it does work. Maybe you’re right, the site might have a block to not allow previews through their Cloudflare account. I was assuming it was our Cloudflare, but maybe it’s theirs.