If you're having trouble with redirection "This page has redirected too many times", check that your SSL mode for the domain is set to "FULL". Traffic to Cloudflare is always encrypted over HTTPS, and this ensures that the traffic between Cloudflare and Backblaze is also encrypted.
The alternative, flexible mode, the communication between Cloudflare and Backblaze is conducted over plain HTTP traffic. Backblaze doesn't allow unencrypted traffic and your browser gets stuck in a redirect loop.
Be aware: Changing this setting to FULL may break other proxied hostnames in your domain if they're not also capable of running over HTTPS independently. If you have any problems, make sure all your proxied hosts have certificates installed (self-signed or otherwise. Free Let's Encrypt certificates work fine). Contact your web host if you don't know what that means. Or turn the SSL mode back to "Flexible" just use the plain Backblaze URL for your offloaded media by setting the Custom URL in Invision to "https://f0002.backblazeb2.com/file/<BUCKET>/" (Whatever your bucket's URL is). You won't get a fancy cdn.yourdomainname.com address, but it should be better supported.
