tomrock wrote:I probably should also mention I'm using Cloudflare to get https.
I don't think it's related. I also use Cloudflare for all our X3 websites, as well as Cloudflare PRO (with cloudflare WAF / firewall) enabled for our main demo. Besides, the error message would look different.
tomrock wrote:What should I do next?
Let me just get this straight: It was working earlier, and then without warning it suddenly wasn't working? I have no reason to believe this is anything else than server/hosting firewall, as several other users have had the same issue.
As stated earlier, you must contact your hosting service and give them the information. If they are professionaly, they will be able to disable the firewall rule that is blocking the legitimate request. If hosts need to run firewalls, without approval or configuration from the user, then this is what they/you will have to deal with. The X3 panel is already behind a login, but the firewall doesn't know that.