A very important factor in running successful scans using Probely is providing clear access to your target.
Having restrictions running without allowing our public IP addresses might lead to failed scans, simply because we got timed out.
There are several reasons why this might be happening:
Since our outbound IP addresses are from a Cloud provider, and traffic produced by humans is not supposed to come from a Cloud provider, they might be blocked by default on your Firewall/WAF.
As a result of the intrusive testing during a scan, your WAF might believe it's an attack block our IP address.
You have a plugin (like Jetpack, Sucuri, Fail2Ban, etc.) that can be actively filtering and blocking our requests;
Our request load (which can spread to multiple threads, making multiple requests per second) caused your firewall to block our IP to prevent spamming, or we could be slowing down your website because of all those requests;
Or maybe there's just a rule configured that we might fit in that can cause our IP to be blocked.
Regardless of that, the best solution to fix this issue is to allow our outbound IP addresses (all updated addresses are in this help article) to freely access your target, by adding them to your infrastructure allow-lists (whitelisting us). If by any chance you have any geo-location restriction in place, please allow Ireland (possibly the EU) since it is where the servers are located.
If you believe that the scans are critically detrimental to your website's performance, please reach out to us, and we'll fine-tune the scanner load to accommodate your needs.