I use a medium sized Australian ISP and got the same, maybe they just have whole regions blocked...?
Probably CGNAT, "Carrier-Grade NAT": https://en.wikipedia.org/wiki/Carrier-grade_NAT
Huge, huge numbers of machines behind a single external IP mean that your internet access carries all their reputation by proxy. Since switching off Comcast to a smaller fiber company that uses CGNAT I've seen somewhat more Cloudflare challenges.
I'm also blocked, but I'm in the UK use a fairly niche and small ISP (uno.uk)
Probably CGNAT, "Carrier-Grade NAT": https://en.wikipedia.org/wiki/Carrier-grade_NAT
Huge, huge numbers of machines behind a single external IP mean that your internet access carries all their reputation by proxy. Since switching off Comcast to a smaller fiber company that uses CGNAT I've seen somewhat more Cloudflare challenges.
I'm also blocked, but I'm in the UK use a fairly niche and small ISP (uno.uk)