I’m unable to re-produce the error shown in your screenshot, but that one means your origin (server behind Cloudflare) isn’t responding to Cloudflare in time.
I would therefore suggest to verify that all Cloudflare IP addresses are allowed in your firewall(s) and security systems.
That said, -
From some locations, I’m able to get a Wordfence block page, that claims “Your access to this site has been temporarily limited by the site owner”.
Sounds to me like you need to restore original visitor IPs:
If you are running multiple security systems on top of each other (which generally isn’t advisable), you will need extreme care to make sure that one of them isn’t interfering with the other(s).