When I try to go to https://voobly.com/forum (the forum link on the voobly.com header) I get into an infinite cloudflare "Verifying you are human. This may take a few seconds." loop, it just waits a few seconds then refreshes the page and shows the same.

However when I open forum directly with a link to a subforum or topic it works fine. Voobly homepage works fine. All other cloudflare sites work fine.

I already tried deleting all voobly.com cookies.

The problem is related to IPv6, you keep getting a new IPv6 with every refresh and Cloudflare sends you a JS challenge. I have this on my cell phone as well.

We use Cloudflare to protect our website from spam bots and DOS attacks.

I have IPv6 disabled in my vpn, so can it still cause this? How come I don't have problems with other cloudflare sites? Is it something in settings that can be changed maybe?

You get the JS challenge every time your IP is changing. Most other Cloudflares don't have this, because they don't have the Enterprise plan. We were or better we are still having major problems with Denial of Service attacks.

working okay again now

Glad to hear it's working for you again.